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DNA calls for the amino acids that make different organisms have different or similar characteristics.

Based on how many similarities and differences organisms have, they are placed on different sections of the taxonomy list.

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we get our features from our parents through DNA.

becuase of DNA and genetics, we can have the same blood types, illness, and even sleep patterns.

Genetics can help us to figure out if we are at risk for any diseases or issues before they appear known to us.

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Perhaps the most fundamental property of all living things is the ability to reproduce. All organisms inherit the genetic information specifying their structure and function from their parents. Likewise, all cells arise from preexisting cells, so the genetic material must be replicated and passed from parent to progeny cell at each cell division. How genetic information is replicated and transmitted from cell to cell and organism to organism thus represents a question that is central to all of biology. Consequently, elucidation of the mechanisms of genetic transmission and identification of the genetic material as DNA were discoveries that formed the foundation of our current understanding of biology at the molecular level.

Genes and Chromosomes

The classical principles of genetics were deduced by Gregor Mendel in 1865, on the basis of the results of breeding experiments with peas. Mendel studied the inheritance of a number of well-defined traits, such as seed color, and was able to deduce general rules for their transmission. In all cases, he could correctly interpret the observed patterns of inheritance by assuming that each trait is determined by a pair of inherited factors, which are now called genes. One gene copy (called an allele) specifying each trait is inherited from each parent. For example, breeding two strains of peas-one having yellow seeds, and the other green seeds-yields the following results ( Figure 3.1). The parental strains each have two identical copies of the gene specifying yellow ( Y) or green ( y) seeds, respectively. The progeny plants are therefore hybrids, having inherited one gene for yellow seeds ( Y) and one for green seeds ( y). All these progeny plants (the first filial, or F ₁, generation) have yellow seeds, so yellow ( Y) is said to be dominant and green ( y) recessive. The genotype (genetic composition) of the F ₁ peas is thus Yy, and their phenotype (physical appearance) is yellow. If one F ₁ offspring is bred with another, giving rise to F ₂ progeny, the genes for yellow and green seeds segregate in a characteristic manner such that the ratio between F ₂ plants with yellow seeds and those with green seeds is 3:1.

Mendel's findings, apparently ahead of their time, were largely ignored until 1900, when Mendel's laws were rediscovered and their importance recognized. Shortly thereafter, the role of chromosomes as the carriers of genes was proposed. It was realized that most cells of higher plants and animals are diploid-containing two copies of each chromosome. Formation of the germ cells (the sperm and egg), however, involves a unique type of cell division ( meiosis) in which only one member of each chromosome pair is transmitted to each progeny cell ( Figure 3.2). Consequently, the sperm and egg are haploid, containing only one copy of each chromosome. The union of these two haploid cells at fertilization creates a new diploid organism, now containing one member of each chromosome pair derived from the male and one from the female parent. The behavior of chromosome pairs thus parallels that of genes, leading to the conclusion that genes are carried on chromosomes.

The fundamentals of mutation, genetic linkage, and the relationships between genes and chromosomes were largely established by experiments performed with the fruit fly, Drosophila melanogaster. Drosophila can be easily maintained in the laboratory, and they reproduce about every two weeks, which is a considerable advantage for genetic experiments. Indeed, these features continue to make Drosophila an organism of choice for genetic studies of animals, particularly the genetic analysis of development and differentiation.

In the early 1900s, a number of genetic alterations ( mutations) were identified in Drosophila, usually affecting readily observable characteristics such as eye color or wing shape. Breeding experiments indicated that some of the genes governing these traits are inherited independently of each other, suggesting that these genes are located on different chromosomes that segregate independently during meiosis ( Figure 3.3). Other genes, however, are frequently inherited together as paired characteristics. Such genes are said to be linked to each other by virtue of being located on the same chromosome. The number of groups of linked genes is the same as the number of chromosomes (four in Drosophila), supporting the idea that chromosomes are carriers of the genes.

Linkage between genes is not complete, however; chromosomes exchange material during meiosis, leading to recombination between linked genes ( Figure 3.4). The frequency of recombination between two linked genes depends on the distance between them on the chromosome; genes that are close to each other recombine less frequently than do genes farther apart. Thus, the frequencies with which different genes recombine can be used to determine their relative positions on the chromosome, allowing the construction of genetic maps ( Figure 3.5). By 1915, nearly a hundred genes had been defined and mapped onto the four chromosomes of Drosophila, leading to general acceptance of the chromosomal basis of heredity.

Genes and Enzymes

Early genetic studies focused on the identification and chromosomal localization of genes that control readily observable characteristics, such as the eye color of Drosophila. How these genes lead to the observed phenotypes, however, was unclear. The first insight into the relationship between genes and enzymes came in 1909, when it was realized that the inherited human disease phenylketonuria (see Molecular Medicine in Chapter 2) results from a genetic defect in metabolism of the amino acid phenylalanine. This defect was hypothesized to result from a deficiency in the enzyme needed to catalyze the relevant metabolic reaction, leading to the general suggestion that genes specify the synthesis of enzymes.

Clearer evidence linking genes with the synthesis of enzymes came from experiments of George Beadle and Edward Tatum, performed in 1941 with the fungus Neurospora crassa. In the laboratory, Neurospora can be grown on minimal or rich media similar to those discussed in Chapter 1 for the growth of E. coli. For Neurospora, minimal media consist only of salts, glucose, and biotin; rich media are supplemented with amino acids, vitamins, purines, and pyrimidines. Beadle and Tatum isolated mutants of Neurospora that grew normally on rich media but could not grow on minimal media. Each mutant was found to require a specific nutritional supplement, such as a particular amino acid, for growth. Furthermore, the requirement for a specific nutritional supplement correlated with the failure of the mutant to synthesize that particular compound. Thus, each mutation resulted in a deficiency in a specific metabolic pathway. Since such metabolic pathways were known to be governed by enzymes, the conclusion from these experiments was that each gene specified the structure of a single enzyme-the one gene-one enzyme hypothesis. Many en-zymes are now known to consist of multiple polypeptides, so the currently accepted statement of this hypothesis is that each gene specifies the structure of a single polypeptide chain.

Identification of DNA as the Genetic Material

Understanding the chromosomal basis of heredity and the relationship between genes and enzymes did not in itself provide a molecular explanation of the gene. Chromosomes contain proteins as well as DNA, and it was initially thought that genes were proteins. The first evidence leading to the identification of DNA as the genetic material came from studies in bacteria. These experiments represent a prototype for current approaches to defining the function of genes by introducing new DNA sequences into cells, as discussed later in this chapter.

The experiments that defined the role of DNA were derived from studies of the bacterium that causes pneumonia ( Pneumococcus). Virulent strains of Pneumococcus are surrounded by a polysaccharide capsule that protects the bacteria from attack by the immune system of the host. Because the capsule gives bacterial colonies a smooth appearance in culture, encapsulated strains are denoted S. Mutant strains that have lost the ability to make a capsule (denoted R) form rough-edged colonies in culture and are no longer lethal when inoculated into mice. In 1928 it was observed that mice inoculated with nonencapsulated (R) bacteria plus heat-killed encapsulated (S) bacteria developed pneumonia and died. Importantly, the bacteria that were then isolated from these mice were of the S type. Subsequent experiments showed that a cell-free extract of S bacteria was similarly capable of converting (or transforming) R bacteria to the S state. Thus, a substance in the S extract (called the transforming principle) was responsible for inducing the genetic transformation of R to S bacteria.

In 1944 Oswald Avery, Colin MacLeod, and Maclyn McCarty established that the transforming principle was DNA, both by purifying it from bacterial extracts and by demonstrating that the activity of the transforming principle is abolished by enzymatic digestion of DNA but not by digestion of proteins ( Figure 3.6). Although these studies did not immediately lead to the acceptance of DNA as the genetic material, they were extended within a few years by experiments with bacterial viruses. In particular, it was shown that, when a bacterial virus infects a cell, the viral DNA rather than the viral protein must enter the cell in order for the virus to replicate. Moreover, the parental viral DNA (but not the protein) is transmitted to progeny virus particles. The concurrence of these results with continuing studies of the activity of DNA in bacterial transformation led to acceptance of the idea that DNA is the genetic material.

The Structure of DNA

Our understanding of the three-dimensional structure of DNA, deduced in 1953 by James Watson and Francis Crick, has been the basis for present-day molecular biology. At the time of Watson and Crick's work, DNA was known to be a polymer composed of four nucleic acid bases-two purines ( adenine [A] and guanine [G]) and two pyrimidines ( cytosine [C] and thymine [T])-linked to phosphorylated sugars. Given the central role of DNA as the genetic material, elucidation of its three-dimensional structure appeared critical to understanding its function. Watson and Crick's consideration of the problem was heavily influenced by Linus Pauling's description of hydrogen bonding and the α helix, a common element of the secondary structure of proteins (see Chapter 2). Moreover, experimental data on the structure of DNA were available from X-ray crystallography studies by Maurice Wilkins and Rosalind Franklin. Analysis of these data revealed that the DNA molecule is a helix that turns every 3.4 nm. In addition, the data showed that the distance between adjacent bases is 0.34 nm, so there are ten bases per turn of the helix. An important finding was that the diameter of the helix is approximately 2 nm, suggesting that it is composed of not one but two DNA chains.

From these data, Watson and Crick built their model of DNA ( Figure 3.7). The central features of the model are that DNA is a double helix with the sugar-phosphate backbones on the outside of the molecule. The bases are on the inside, oriented such that hydrogen bonds are formed between purines and pyrimidines on opposite chains. The base pairing is very specific: A always pairs with T and G with C. This specificity accounts for the earlier results of Erwin Chargaff, who had analyzed the base composition of various DNAs and found that the amount of adenine was always equal to that of thymine, and the amount of guanine to that of cytosine. Because of this specific base pairing, the two strands of a DNA molecule are complementary: Each strand contains all the information required to specify the sequences of bases on the other.

Replication of DNA

The discovery of complementary base pairing between DNA strands immediately suggested a molecular solution to the question of how the genetic material could direct its own replication-a process that is required each time a cell divides. It was proposed that the two strands of a DNA molecule could separate and serve as templates for synthesis of new complementary strands, the sequence of which would be dictated by the specificity of base pairing ( Figure 3.8). The process is called semiconservative replication because one strand of parental DNA is conserved in each progeny DNA molecule.

Direct support for semiconservative DNA replication was obtained in 1958 as a result of elegant experiments, performed by Matthew Meselson and Frank Stahl, in which DNA was labeled with isotopes that altered its density ( Figure 3.9). E. coli were first grown in media containing the heavy isotope of nitrogen ( ¹⁵N) in place of the normal light isotope ( ¹⁴N). The DNA of these bacteria consequently contained ¹⁵N and was heavier than that of bacteria grown in ¹⁴N. Such heavy DNA could be separated from DNA containing ¹⁴N by equilibrium centrifugation in a density gradient of CsCl. This ability to separate heavy ( ¹⁵N) DNA from light ( ¹⁴N) DNA enabled the study of DNA synthesis. E. coli that had been grown in ¹⁵N were transferred to media containing ¹⁴N and allowed to replicate one more time. Their DNA was then extracted and analyzed by CsCl density gradient centrifugation. The results of this analysis indicated that all of the heavy DNA had been replaced by newly synthesized DNA with a density intermediate between that of heavy ( ¹⁵N) and that of light ( ¹⁴ N) DNA molecules. The implication was that during replication, the two parental strands of heavy DNA separated and served as templates for newly synthesized progeny strands of light DNA, yielding double-stranded molecules of intermediate density. This experiment thus provided direct evidence for semiconservative DNA replication, clearly underscoring the importance of complementary base pairing between strands of the double helix.

The ability of DNA to serve as a template for its own replication was further established with the demonstration that an enzyme purified from E. coli ( DNA polymerase) could catalyze DNA replication in vitro. In the presence of DNA to act as a template, DNA polymerase was able to direct the incorporation of nucleotides into a complementary DNA molecule.

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Perhaps the most fundamental property of all living things is the ability to reproduce. All organisms inherit the genetic information specifying their structure and function from their parents. Likewise, all cells arise from preexisting cells, so the genetic material must be replicated and passed from parent to progeny cell at each cell division.

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Ecological Pyramids - Definition, Types, Examples, Importance, Limitations - Biology Notes Online

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-Without proteins--which are made from DNA--we would not have any biodiversity to have Ecological pyramids or even see any differences between animals

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Ecological Pyramids - Definition, Types, Examples, Importance, Limitations - Biology Notes Online

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Ecological pyramids are graphical representations that depict the distribution of energy, biomass, or numbers of organisms across different trophic levels in

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How DNA relates to evolution (Natalie & Abby)

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How DNA relates to evolution (Natalie & Abby)

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-Mutations in DNA create different animal as well as different looks.

-Mutations in the DNA can cause the animals to act different and can lead to new behaviors.

-Mutations can give animals something that helps them survive better. This can lead to other species dying off.

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Raymond - University of Hong Kong: PhD in Molecular Biology

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How does DNA replication contribute to evolutionary change? | TutorChase

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Need help understanding how DNA replication contributes to evolutionary change? Expert tutors answering your Biology questions!

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-Shows how different parts of DNA bond to one another

-Talks about the base pairing rule

-Shows that As go with Ts and Gs go with Cs

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Base pairing interactive, interactive 2D animation :: CSHL DNA Learning Center

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Be James Watson; match the base pairs in this interactive game.

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How ecology relates to DNA (Jazlyn and Bella B)

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How ecology relates to DNA (Jazlyn and Bella B)

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How does ecology and dna relate? - Ecology today

Ecological factors affect DNA adaptation.

Allows researchers to build up a far more detailed understanding of the species through DNA.

Phenotypes can change due to the ecological patterns.

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The ecology of environmental DNA and implications for conservation genetics - Conservation Genetics

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Environmental DNA (eDNA) refers to the genetic material that can be extracted from bulk environmental samples such as soil, water, and even air. The rapidly expanding study of eDNA has generated unprecedented ability to detect species and conduct genetic analyses for conservation, management, and research, particularly in scenarios where collection of whole organisms is impractical or impossible. While the number of studies demonstrating successful eDNA detection has increased rapidly in recent years, less research has explored the “ecology” of eDNA—myriad interactions between extraorganismal genetic material and its environment—and its influence on eDNA detection, quantification, analysis, and application to conservation and research. Here, we outline a framework for understanding the ecology of eDNA, including the origin, state, transport, and fate of extraorganismal genetic material. Using this framework, we review and synthesize the findings of eDNA studies from diverse environments, taxa, and fields of study to highlight important concepts and knowledge gaps in eDNA study and application. Additionally, we identify frontiers of conservation-focused eDNA application where we see the most potential for growth, including the use of eDNA for estimating population size, population genetic and genomic analyses via eDNA, inclusion of other indicator biomolecules such as environmental RNA or proteins, automated sample collection and analysis, and consideration of an expanded array of creative environmental samples. We discuss how a more complete understanding of the ecology of eDNA is integral to advancing these frontiers and maximizing the potential of future eDNA applications in conservation and research.

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mitosis splits the dna

the genetic information (DNA) is what makes the identical daughter cell

DNA replication happens during s phase

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Most cells grow, perform the activities needed to survive, and divide to create new cells. These basic processes, known collectively as the cell cycle, are repeated throughout the life of a cell. Of the various parts of the cell cycle, the division portion is particularly important, because this is the point at which a cell passes its genetic information to its offspring cells. In many situations, division also ensures that new cells are available to replace the older cells within an organism whenever those cells die.

Prokaryotic cells, which include bacteria, undergo a type of cell division known as binary fission. This process involves replication of the cell's chromosomes, segregation of the copied DNA, and splitting of the parent cell's cytoplasm. The outcome of binary fission is two new cells that are identical to the original cell.

In contrast to prokaryotic cells, eukaryotic cells may divide via either mitosis or meiosis. Of these two processes, mitosis is more common. In fact, whereas only sexually reproducing eukaryotes can engage in meiosis, all eukaryotes - regardless of size or number of cells - can engage in mitosis. But how does this process proceed, and what sorts of cells does it produce?

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Replication and Distribution of DNA during Mitosis

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Most cells grow, perform the activities needed to survive, and divide to create new cells. These basic processes, known collectively as the cell cycle, are repeated throughout the life of a cell. Of the various parts of the cell cycle, the division portion is particularly important, because this is the point at which a cell passes its genetic information to its offspring cells.

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most DNA is found in the nucleus

some dna is found in the mitochondria

also the information gets packaged and moved on, this is when we learned about the location and functions of organelles

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-Shows the interactions between genes and the environment

- talks a little about the mutations in genes help cause allergies

-talks about ecology some as well which we talked about in the past

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National Institute of Environmental Health Sciences

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Introduction

Few diseases result from a change in a single gene or even multiple genes. Instead, most diseases are complex and stem from an interaction between your genes and your environment. Factors in your environment can range from chemicals in air or water pollution, mold, pesticides, diet choices, or grooming products.

Subtle differences in one person's genes can cause them to respond differently to the same environmental exposure as another person. As a result, some people may develop a disease after being exposed to something in the environment while others may not.

As scientists learn more about the connection between genes and the environment, they pursue new approaches for preventing and treating disease that consider individual genetic codes.

What is NIEHS Doing?

NIEHS studies a wide range of diseases and disorders with genetic and environmental components. In addition, new technologies and computational approaches are under development to tease out the gene and environment interactions that underpin disease.

Autism - High levels of air pollution increase the risk for autism in children with a genetic variant called MET, which is involved in brain development. This genetic variant did not increase the risk for the 75% of the population exposed to lower levels of air pollution, suggesting that autism may be caused by an interaction of genetic and environmental factors.

DNA Repair - Molecules damaged by environmental exposures like ultraviolet light or certain chemicals are incorporated into DNA, triggering cell death that may lead to cancer, diabetes, hypertension, cardiovascular and lung disease, and Alzheimer's disease.

Metabolism - Researchers in the NIEHS Metabolism, Genes, and Environment Group discovered that a protein called SIRT1, which plays a critical role in early development and metabolism, could provide the basis for therapeutic targets for metabolic diseases and aging at the genetic level.

Parkinson's disease - The chance of developing Parkinson's disease after pesticide exposure was greater in people who had a genetic variation that affected the production of nitric oxide, a molecule that can damage neurons. Lifestyle choices related to diet, exercise, and nicotine use also have been linked to the chance of developing Parkinson's disease.

Respiratory Syncytial Virus (RSV) - An international study that included NIEHS scientists discovered children with variations in a gene called TLR4 who were exposed to certain environmental factors developed severe cases of RSV bronchiolitis, a life-threatening respiratory disease.

New data analysis methods - Many studies can only analyze one type of environmental exposure at a time, which does not account for combined effects of multiple exposures and genes acting together. But, a computational approach by NIEHS-funded researchers can simultaneously analyze data on multiple environmental exposures and their interactions with genes. Researchers used data about atherosclerosis, a chronic heart condition, as a test case for the method's application in future studies.

Monitoring the state of the field - NIEHS helped convene a workshop, "Current Challenges and New Opportunities for Gene-Environment Interaction Studies of Complex Diseases," to explore issues surrounding study of the interplay between genes and the environment. Attendees found that along with research challenges many exciting opportunities exist for new studies.

Further Reading

Stories from the Environmental Factor (NIEHS Newsletter)

Fact Sheets

Additional Resources

Related Health Topics

This content is available to use on your website.

Please visit NIEHS Syndication to get started.

Autism - High levels of air pollution increase the risk for autism in children with a genetic variant called MET, which is involved in brain development. This genetic variant did not increase the risk for the 75% of the population exposed to lower levels of air pollution, suggesting that autism may be caused by an interaction of genetic and environmental factors.

DNA Repair - Molecules damaged by environmental exposures like ultraviolet light or certain chemicals are incorporated into DNA, triggering cell death that may lead to cancer, diabetes, hypertension, cardiovascular and lung disease, and Alzheimer's disease.

Metabolism - Researchers in the NIEHS Metabolism, Genes, and Environment Group discovered that a protein called SIRT1, which plays a critical role in early development and metabolism, could provide the basis for therapeutic targets for metabolic diseases and aging at the genetic level.

Parkinson's disease - The chance of developing Parkinson's disease after pesticide exposure was greater in people who had a genetic variation that affected the production of nitric oxide, a molecule that can damage neurons. Lifestyle choices related to diet, exercise, and nicotine use also have been linked to the chance of developing Parkinson's disease.

Respiratory Syncytial Virus (RSV) - An international study that included NIEHS scientists discovered children with variations in a gene called TLR4 who were exposed to certain environmental factors developed severe cases of RSV bronchiolitis, a life-threatening respiratory disease.

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Few diseases result from a change in a single gene or even multiple genes. Instead, most diseases are complex and stem from an interaction between your genes and your environment.

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DNA contains the needed instructions for organisms to grow and reproduce

the DNA sequences must be converted to messages so the organism can use it

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In organisms called eukaryotes, DNA is found inside a special area of the cell called the nucleus. Because the cell is very small, and because organisms have many DNA molecules per cell, each DNA molecule must be tightly packaged. This packaged form of the DNA is called a chromosome.

During DNA replication, DNA unwinds so it can be copied. At other times in the cell cycle, DNA also unwinds so that its instructions can be used to make proteins and for other biological processes. But during cell division, DNA is in its compact chromosome form to enable transfer to new cells.

Researchers refer to DNA found in the cell's nucleus as nuclear DNA. An organism's complete set of nuclear DNA is called its genome.

Besides the DNA located in the nucleus, humans and other complex organisms also have a small amount of DNA in cell structures known as mitochondria. Mitochondria generate the energy the cell needs to function properly.

In sexual reproduction, organisms inherit half of their nuclear DNA from the male parent and half from the female parent. However, organisms inherit all of their mitochondrial DNA from the female parent. This occurs because only egg cells, and not sperm cells, keep their mitochondria during fertilization.

DNA is made of chemical building blocks called nucleotides. These building blocks are made of three parts: a phosphate group, a sugar group and one of four types of nitrogen bases. To form a strand of DNA, nucleotides are linked into chains, with the phosphate and sugar groups alternating.

The four types of nitrogen bases found in nucleotides are: adenine (A), thymine (T), guanine (G) and cytosine (C). The order, or sequence, of these bases determines what biological instructions are contained in a strand of DNA. For example, the sequence ATCGTT might instruct for blue eyes, while ATCGCT might instruct for brown.

The complete DNA instruction book, or genome, for a human contains about 3 billion bases and about 20,000 genes on 23 pairs of chromosomes.

DNA contains the instructions needed for an organism to develop, survive and reproduce. To carry out these functions, DNA sequences must be converted into messages that can be used to produce proteins, which are the complex molecules that do most of the work in our bodies.

Each DNA sequence that contains instructions to make a protein is known as a gene. The size of a gene may vary greatly, ranging from about 1,000 bases to 1 million bases in humans. Genes only make up about 1 percent of the DNA sequence. DNA sequences outside this 1 percent are involved in regulating when, how and how much of a protein is made.

DNA's instructions are used to make proteins in a two-step process. First, enzymes read the information in a DNA molecule and transcribe it into an intermediary molecule called messenger ribonucleic acid, or mRNA.

Next, the information contained in the mRNA molecule is translated into the "language" of amino acids, which are the building blocks of proteins. This language tells the cell's protein-making machinery the precise order in which to link the amino acids to produce a specific protein. This is a major task because there are 20 types of amino acids, which can be placed in many different orders to form a wide variety of proteins.

The Swiss biochemist Frederich Miescher first observed DNA in the late 1800s. But nearly a century passed from that discovery until researchers unraveled the structure of the DNA molecule and realized its central importance to biology.

For many years, scientists debated which molecule carried life's biological instructions. Most thought that DNA was too simple a molecule to play such a critical role. Instead, they argued that proteins were more likely to carry out this vital function because of their greater complexity and wider variety of forms.

The importance of DNA became clear in 1953 thanks to the work of James Watson*, Francis Crick, Maurice Wilkins and Rosalind Franklin. By studying X-ray diffraction patterns and building models, the scientists figured out the double helix structure of DNA - a structure that enables it to carry biological information from one generation to the next.

* James Watson was the first NHGRI Director and appears here as part of our history collection. Despite his scientific achievements, Dr. Watson's career was also punctuated by a number of offensive and scientifically erroneous comments about his beliefs on race, nationalities, homosexuality, gender, and other societal topics. Dr. Watson's opinions on these topics are unsupported by science and are counter to the mission and values of NHGRI.

Scientist use the term "double helix" to describe DNA's winding, two-stranded chemical structure. This shape - which looks much like a twisted ladder - gives DNA the power to pass along biological instructions with great precision.

To understand DNA's double helix from a chemical standpoint, picture the sides of the ladder as strands of alternating sugar and phosphate groups - strands that run in opposite directions. Each "rung" of the ladder is made up of two nitrogen bases, paired together by hydrogen bonds. Because of the highly specific nature of this type of chemical pairing, base A always pairs with base T, and likewise C with G. So, if you know the sequence of the bases on one strand of a DNA double helix, it is a simple matter to figure out the sequence of bases on the other strand.

DNA's unique structure enables the molecule to copy itself during cell division. When a cell prepares to divide, the DNA helix splits down the middle and becomes two single strands. These single strands serve as templates for building two new, double-stranded DNA molecules - each a replica of the original DNA molecule. In this process, an A base is added wherever there is a T, a C where there is a G, and so on until all of the bases once again have partners.

In addition, when proteins are being made, the double helix unwinds to allow a single strand of DNA to serve as a template. This template strand is then transcribed into mRNA, which is a molecule that conveys vital instructions to the cell's protein-making machinery.

Current Slide Current Slide

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Deoxyribonucleic acid (DNA) is a molecule that contains the biological instructions that make each species unique.

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Sequencing DNA allows scientists to categorize organisms accurately.

Taxonomy is important since other scientific disciplines like conservation and drug discovery hinge on organisms being classified and named.

Taxonomy uses hierarchical classification as a way to help scientists understand and organize the diversity of life on our planet.

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Carissa Shipman explains the role genetic information now plays in the classification of living things.

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-Explains the importance of DNA in mitosis

- Kind of goes into detail of DNA structure

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Replication and Distribution of DNA during Mitosis | Learn Science at Scitable

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What Can DNA in the Environment Tell Us About an Ecosystem?

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What Can DNA in the Environment Tell Us About an Ecosystem?

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-Substances found in the environment, such as water, soil, or saliva, can contain DNA from the species living there. This DNA can come from the hair, scales, skin, saliva or waste products of the organisms in that environment. DNA collected from the environment is called environmental DNA.

-From studies of eDNA, the number of known organisms sharing our planet has increased substantially

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Abstract

Scientists estimate that we share this planet with millions of other species! But how do we know which species are out there and how can we keep track of them? Unfortunately, humans are driving lots of species to extinction and disrupting important natural ecosystems. It is now more important than ever that we understand which species are present in different places and the roles they play in their ecosystems. With this knowledge, we can figure out how to protect important organisms and their habitats. Exciting new technology has made it possible to identify species using DNA that they have released into the environment-this is known as environmental DNA (eDNA). Scientists are now using eDNA to identify species in all kinds of ecosystems across the world. In this article, we explain how eDNA is used to detect species and describe the advantages and disadvantages of this method.

Monitoring Biodiversity is Important

Humans are having an increasing impact on global , which means our actions are reducing the total number of different species present on the planet. Many species are being driven to extinction before we even know anything about them or understand the roles they play in the environment. The loss of key species or the arrival of can change an ecosystem forever [, ]. Because of this, studies of biodiversity are becoming increasingly important, so we can understand how various ecosystems are changing.

Traditionally, scientists have monitored ecosystems by physically exploring those locations, identifying the species living there based on how the organisms look, and counting the organisms []. This type of traditional monitoring requires the expert knowledge of scientists called taxonomists, who specialize in identifying species by closely analyzing them. Unfortunately, the number of scientists with these skills is declining, especially those who can identify rare species, which means that studies of biodiversity often are not as in-depth or as extensive as they should be.

As technology has improved, scientists have found another way to identify the species present in ecosystems-DNA. DNA basically contains the blueprint for every living organism, determining how each organism looks and functions. DNA is made up of two strands containing a combination of four chemicals called (cytosine [C], guanine [G], adenine [A], or thymine [T]) wound into a twisted, helical structure. Parts of the DNA sequence can act as "barcodes," which can help identify different species. This means that, by looking at a certain part of an organism's DNA, scientists can identify the organism.

What is eDNA?

Over the last 30 years, scientists have started using DNA barcodes to investigate which species are found in different environments. Substances found in the environment, such as water, soil, saliva, or faeces (poop) can contain DNA from the species living there. This DNA can come from the hair, scales, skin, saliva or waste products of the organisms in that environment. DNA collected from the environment is called environmental DNA (eDNA). Analysis of eDNA is rapidly changing the way scientists study ecosystems and biodiversity [].

How Can eDNA be Used to Identify the Organisms in a Community?

A community is made up of many different species. To identify the species making up a community in a certain ecosystem, samples are taken from the environment and analyzed for eDNA. Specific short fragments of eDNA from the environment are multiplied using a process called polymerase chain reaction (PCR), so that there are enough of them to study. PCR makes thousands of copies of these DNA sequences from all the species in the sample. Since each species has a specific code made up of the four bases (A, C, G, or T), these short sequences can act as identifiers for different species-much like a barcode identifies an item in a shop. machines can read the order of these bases in the DNA. Once the barcode sequences are known, they can be matched with sequences in a database of known species. This way, the organisms present in the ecosystem can be identified ( Figure 1).

Figure 1 - How environmental DNA (eDNA) can be used to identify species.

(A) Samples are collected from the environment (e.g., water, soil, feces). (B) eDNA from organisms in each sample is extracted (removed) from the samples. (C) DNA sequences from the samples are multiplied through a method called PCR, so that there are enough sequences to study. (D) The sequences are then read on a sequencing machine, showing the order of bases on the DNA strands. (E) Sequences are then matched to known sequences in worldwide databases. (F) A list is produced of species found in that environment!

What Are the Advantages of Using eDNA to Identify Species?

DNA-based methods have revolutionized the study of species that are hard to see and identify using traditional methods []. For example, most bacterial species look the same-like rods or spheres-making identification based on what they look like almost impossible. But scientists can tell these bacteria apart using eDNA. In fact, scientists did not even realize how many diverse species of bacteria there are until eDNA studies became common. Identifying species when they are young is often harder than when looking at their adult stage-think of frogs and tadpoles. Frogs of different species can look very different but often the tadpoles which they develop from look very similar. The ability to determine which species a juvenile belongs to is very important for understanding the habitats that a species relies on for its different developmental stages. This knowledge can help scientists make the right decisions to help protect a species' habitat and preserve biodiversity. There are other reasons it is often difficult to detect species in the environment. Many species are good at hiding. Some can change the way they look in different environmental conditions, or they might live in habitats where they are difficult to see. For example, many invertebrates take shelter in coral reefs, and many species live in the dark depths of oceans or lakes. With the help of eDNA, the diversity present in many of the world's hidden ecosystems is being revealed.

is one field in which eDNA is being used. Conservation biology is the protection and conservation of species and their habitats. In this field, eDNA can both help to detect rare species and identify invasive species. Traditional monitoring to detect rare species is time consuming and often requires work in remote parts of the world, so eDNA provides an advantage. One interesting example of the use of eDNA comes from the study of rare vertebrates. Finding these rare animals is difficult, but eDNA can be obtained from the stomach contents of parasites like leeches and mosquitoes that feed on the rare animals, and these parasites are easier to find. eDNA can tell scientists which species the parasites have been feeding on, which can tell scientists if rare species are present in the area. eDNA can also be used as an early-warning system to identify invasive species as they spread into new environments. Because eDNA can detect species even when there are very few individuals in the environment, it can help us respond quickly to the threat of an invasive species. This means there is a greater chance of stopping the spread of an invasive species before it becomes established and potentially harms native species.

It is often less expensive to identify organisms using eDNA than it is to identify them using traditional methods [], and eDNA samples can often be processed faster. This means that more samples can be taken over a wider range of space and time, allowing for in-depth studies and better knowledge of the species that are present in an ecosystem ( Figure 2).

Figure 2 - Advantages of studying biodiversity using eDNA.

Usine eDNA can reduce time and cost compared with traditional identification methods. This means that eDNA studies can be more in-depth and cover larger areas or longer time scales. eDNA can also be better at identifying hidden organisms or juveniles, which means more species can often be found than when using tradition methods.

Are There Any Problems With Using eDNA?

Using eDNA to find species has helped us get a clearer picture of what is living on our planet, how many different species are living together, and how communities of organisms change over time. However, this technique still has three main limitations.

The first limitation of using eDNA to identify species is that, during the PCR reaction or the DNA sequencing process, sometimes mistakes can be made, preventing the DNA sequence from being copied or read properly. These errors could lead to a species being mis-identified. For example, a species could either be missed when it is present (a false negative) or be identified as being present in a sample when it does not actually exist (a false positive).

Also, traditional methods of assessing biodiversity usually involve counting the number of organisms present in a sample, along with identifying which species are present. eDNA helps scientists know the number of different species found in a community. However, it does not tell them how many individual members of that species are present in that ecosystem, the way traditional counting would. Even if there is more DNA from a certain species, that does not necessarily mean there are more members of that species present. So, eDNA cannot be relied upon to give an accurate estimate of the number of organisms in a community.

One last potential limitation of using eDNA is that it might cause species to be identified incorrectly. To correctly identify an unknown species from a DNA sequence, the sequence is compared with a huge database containing barcodes of known organisms. This is done based on similarity-if the new sequence matches exactly with a known sequence, it is said to belong to that species. Unfortunately, the databases are incomplete because not all known species have been sequenced yet, so some sequences obtained from eDNA cannot be exactly matched to a known sequence. If the sequences do not exactly match an organism in the database, they are assigned to the closest matching sequence, which can sometimes be a quite different organism!

The Future of eDNA

Environmental DNA has helped reveal the enormous biodiversity existing on Earth. From studies of eDNA, the number of known organisms sharing our planet has increased substantially! eDNA methods are an incredible advancement in species detection, but there are still some issues that scientists need to work out. But, this field is progressing quickly and these techniques will become even more powerful and important in the future. So far, eDNA has given us a better picture of what species live on this Earth and the roles they play in their ecosystem, which means we can have a better idea of how to protect and conserve the world around us.

Glossary

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Acknowledgments

The authors acknowledge the support of the New Zealand Ministry of Business, Innovation, and Employment research programmes-Our lakes' health; past, present, and future (C05X1707) & A toolbox to underpin and enable tomorrow's marine biosecurity system New Zealand (CAWX1904)-as well as the University of Otago Ph.D. scholarship held by LS. We thank the reviewers, Science Mentor, and editor for their valuable and constructive comments. Finally we would also like to thank Susan Debad for making our manuscript more accessible to a young audience.

References

[1] ↑ Babić, I., Hudina, S., and Bielen, A. 2017. Invasion of the Chinese pond mussels-what makes these harmless-looking animals so dangerous? Front. Young Minds 5:56. doi: 10.3389/frym.2017.00056

[2] ↑ Giovos, I., Katsanevakis, S., Coll, M., Piroddi, C., Steenbeek, J., Lasram, F. B. R., et al. 2019. Human activities help alien species to invade the Mediterranean sea. Front. Young Minds 7:97. doi: 10.3389/frym.2019.00097

[3] ↑ Berkes, F., Colding, J., and Folke, C. 2000. Rediscovery of traditional ecological knowledge as adaptive management. Ecol. Appl. 10:1251-62. doi: 10.2307/2641280

[4] ↑ Taberlet, P., Bonin, A., Zinger, L., and Coissac, E. 2018. Environmental DNA: For Biodiversity Research and Monitoring. Oxford, UK: Oxford University Press.

[5] ↑ Hebert, P. D. N., and Gregory, T. R. 2005. The promise of DNA barcoding for taxonomy. Syst. Biol. 54:852-9. doi: 10.1080/10635150500354886

[6] ↑ Thomsen, P. F., and Willerslev, E. 2015. Environmental DNA-an emerging tool in conservation for monitoring past and present biodiversity. Biol. Conserv. 183:4-18. doi: 10.1016/j.biocon.2014.11.019

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What Can DNA in the Environment Tell Us About an Ecosystem?

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Scientists estimate that we share this planet with millions of other species! But how do we know which species are out there and how can we keep track of them?

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By analyzing DNA, scientists can figure out the kinds of animals that live on our planet, where they live, and the ways in which they’re related.

Scientists travel around the world to observe many different animal species and to collect their DNA.

This helps protect endangered animals and the habitats they live in.

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Scientists travel around the world to observe many different animal species and to collect their . By analyzing DNA, scientists can figure out the kinds of animals that live on our planet, where they live, and the ways in which they're related. This information helps protect endangered animals and the habitats they live in.

Check out these scientists' journals from around the world!

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Scientists travel around the world to observe many different animal species and to collect their . By analyzing DNA, scientists can figure out the kinds of animals that live on our planet, where they live, and the ways in which they're related. This information helps protect endangered animals and the habitats they live in.

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-Mitosis is used to produce daughter cells that are genetically identical to the parent cells.

-The cell copies - or 'replicates' - its chromosomes

-splits the copied chromosomes equally to make sure that each daughter cell has a full set

-DNA is in mitosis

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-We learned about how species are grouped in ecology and how the environment interacts with each other

-DNA, especially eDNA, helps scientists understand biodiversity, track species, and monitor ecosystems by analyzing DNA shed into the environment.

-eDNA can be used to assess the biodiversity of an area by identifying the species present in a sample of water, soil, or air.

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How does cancer relate to a mutation in the DNA?

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How does cancer relate to a mutation in the DNA?

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-Genetic mutations can be inherited from a parent meaning a person has always had the mutation, but they can also happen at any time during a person's life.

-An acquired gene mutation is not inherited from a parent.

-If these genes aren’t working properly, it can affect cancer risk.

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Mutations are abnormal changes in the DNA of a gene and can sometimes lead to cancer. Find out common causes.

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-We have learned about what happens during cellular respiration and that is what this is all about

-we also learned about how it is different from photosynthesis which is discusssed in the article.

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Why are protein important to our body? Willow Smith

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Why are protein important to our body? Willow Smith

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Proteins are important parts of your body and daily needs. They help with the building of DNA.

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What is the relationship between DNA, RNA and proteins? | AAT Bioquest

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What is the relationship between DNA, RNA and proteins?

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They insert you own DNA replication to protect and help your immune system.

They do not carry enzymes, so they do not affect your DNA.

They also help our chromosomes.

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Some of the COVID-19 vaccines use messenger RNA to provoke an immune response. But what exactly is this genetic material, and how does it interact with the DNA in our cells?

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-It talks about ph levels and we learned about that in the biochemistry unit

-we learned about the function of an enzyme and that it what this discusses

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What are enzymes?

Enzymes are proteins that help speed up metabolism, or the chemical reactions in our bodies. They build some substances and break others down. All living things have enzymes.

Our bodies naturally produce enzymes. But enzymes are also in manufactured products and food.

What do enzymes do?

One of the most important roles of enzymes is to aid in digestion. Digestion is the process of turning the food we eat into energy. For example, there are enzymes in our saliva, pancreas, intestines and stomach. They break down fats, proteins and carbohydrates. Enzymes use these nutrients for growth and cell repair.

Enzymes also help with:

Breathing.

Building muscle.

Nerve function.

Ridding our bodies of toxins.

What are the different types of enzymes?

There are thousands of individual enzymes in the body. Each type of enzyme only has one job. For example, the enzyme sucrase breaks down a sugar called sucrose. Lactase breaks down lactose, a kind of sugar found in milk products.

Some of the most common digestive enzymes are:

Carbohydrase breaks down carbohydrates into sugars.

Lipase breaks down fats into fatty acids.

Protease breaks down protein into amino acids.

Parts of Enzymes

What are the parts of an enzyme?

Each enzyme has an "active site." This area has a unique shape. The substance an enzyme works on is a substrate. The substrate also has a unique shape. The enzyme and the substrate must fit together to work.

How do temperature and pH affect enzymes?

Enzymes need the right conditions to work. If conditions aren't right, enzymes can change shape. Then, they no longer fit with substrates, so they don't work correctly.

Each enzyme has an ideal temperature and pH:

pH: Enzymes are sensitive to acidity and alkalinity. They don't work properly if an environment is too acidic or basic. For example, an enzyme in the stomach called pepsin breaks down proteins. If your stomach doesn't have enough acid, pepsin can't function optimally.

Temperature: Enzymes work best when your body temperature is normal, about 98.6°F (37°C). As temperature increases, enzyme reactions increase. But if the temperature gets too high, the enzyme stops working. That's why a high fever can disrupt bodily functions.

Common Conditions & Disorders

What health conditions can enzyme problems cause?

Metabolic disorders are often the result of not having enough of a certain enzyme. Parents can pass them to their children through genes (inherited). Some examples of inherited metabolic disorders include:

Fabry disease prevents body from making enzymes (alpha-galactosidase A) that break down fat (lipids).

Krabbe disease (globoid cell leukodystrophy) affects enzymes needed for the protective covering (myelin) on nerve cells (Central Nervous System).

Maple syrup urine disease affects enzymes needed to break down certain branch chain amino acids.

Other health conditions related to enzyme imbalances include:

Crohn's disease an imbalance of the bacteria in your gut (gut microbiome) may influence an autoimmune response of the intestinal tract. This may play a role in presentation and severity of Crohn's disease.

Exocrine pancreatic insufficiency (EPI) is a condition where your pancreas doesn't have enough digestive enzymes. You can't break down food or absorb nutrients. Chronic pancreatitis, pancreatic cancer, diabetes or cystic fibrosis can lead to EPI.

Lactose intolerance is a shortage of the enzyme needed to digest sugars in milk (lactose) and dairy.

How are enzyme tests used to diagnose health conditions?

Your healthcare provider can use a variety of enzyme and protein blood tests to check for certain health conditions. For example, elevated liver enzymes could be a sign of liver disease.

Caring for Your Enzymes

Do I need to take enzyme supplements?

People without chronic health conditions can usually get the enzymes they need from a healthy diet. But, if you have certain health conditions, your healthcare provider may recommend taking enzyme supplements. For instance, many people with EPI may take a digestive enzyme before they eat. This helps their bodies absorb nutrients from food. Talk to your healthcare provider before taking any type of enzyme supplement.

Can medications affect enzyme levels?

Some medications affect enzyme levels. For example, antibiotics can kill certain bacteria needed for some enzymes to work their best. This is the reason antibiotics may cause diarrhea. To kill the bacteria making you sick, they also wipe out important good bacteria that aid in digestion.

Statins (medications that lower cholesterol) can raise liver enzymes and muscle enzymes. They may increase the risk of damage to the liver or muscles.

When to Call a Doctor

When should I contact my doctor about an enzyme problem?

You won't know if you have an enzyme problem without a blood test. Contact your doctor if you experience any of the following problems:
A note from Cleveland Clinic
Enzymes help facilitate biochemical reactions in our bodies. They aid in everything from breathing to digestion. Having too little or too much of a certain enzyme can lead to health problems. Some people with chronic conditions may need to take enzyme supplements to help their bodies work as they should. Only take enzyme supplements under the supervision of your healthcare provider.

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Enzymes: What Are Enzymes, Pancreas, Digestion & Liver Function

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Enzymes aid chemical reactions in our bodies. They help with digestion, liver function and more. Enzyme imbalances cause health problems.

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-DNA replication occurs during S-phase

-The process of mitosis as a whole is also similar to DNA replication because they both split and create a new version

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Most cells grow, perform the activities needed to survive, and divide to create new cells. These basic processes, known collectively as the cell cycle, are repeated throughout the life of a cell. Of the various parts of the cell cycle, the division portion is particularly important, because this is the point at which a cell passes its genetic information to its offspring cells. In many situations, division also ensures that new cells are available to replace the older cells within an organism whenever those cells die.

Prokaryotic cells, which include bacteria, undergo a type of cell division known as binary fission. This process involves replication of the cell's chromosomes, segregation of the copied DNA, and splitting of the parent cell's cytoplasm. The outcome of binary fission is two new cells that are identical to the original cell.

In contrast to prokaryotic cells, eukaryotic cells may divide via either mitosis or meiosis. Of these two processes, mitosis is more common. In fact, whereas only sexually reproducing eukaryotes can engage in meiosis, all eukaryotes - regardless of size or number of cells - can engage in mitosis. But how does this process proceed, and what sorts of cells does it produce?

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Replication and Distribution of DNA during Mitosis

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Most cells grow, perform the activities needed to survive, and divide to create new cells. These basic processes, known collectively as the cell cycle, are repeated throughout the life of a cell. Of the various parts of the cell cycle, the division portion is particularly important, because this is the point at which a cell passes its genetic information to its offspring cells.

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DNA unit to Macromolecule unit (Rosi and Larkin)

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DNA unit to Macromolecule unit (Rosi and Larkin)

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-DNA is a macromolecule

-DNA eventually makes proteins and proteins are a macromolecule

-Amino acids help make proteins and amino acids are the monomers of proteins

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-we have talked about gene trees where you see how other species are

-The genetic trees are based on what is on way that there genes are built

-The genes are also based on the people who can before them

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A phylogenetic tree is a diagram that represents evolutionary relationships among organisms. Phylogenetic trees are hypotheses, not definitive facts.

The pattern of branching in a phylogenetic tree reflects how species or other groups evolved from a series of common ancestors.

In trees, two species are more related if they have a more recent common ancestor and less related if they have a less recent common ancestor.

Phylogenetic trees can be drawn in various equivalent styles. Rotating a tree about its branch points doesn't change the information it carries.

Introduction

Humans as a group are big on organizing things. Not necessarily things like closets or rooms; I personally score low on the organization front for both of those things. Instead, people often like to group and order the things they see in the world around them. Starting with the Greek philosopher Aristotle, this desire to classify has extended to the many and diverse living things of Earth.

Most modern systems of classification are based on evolutionary relationships among organisms - that is, on the organisms' phylogeny. Classification systems based on phylogeny organize species or other groups in ways that reflect our understanding of how they evolved from their common ancestors.

In this article, we'll take a look at phylogenetic trees, diagrams that represent evolutionary relationships among organisms. We'll see exactly what we can (and can't!) infer from a phylogenetic tree, as well as what it means for organisms to be more or less related in the context of these trees.

Anatomy of a phylogenetic tree

When we draw a phylogenetic tree, we are representing our best hypothesis about how a set of species (or other groups) evolved from a common ancestor. As we'll explore further in the article on building trees, this hypothesis is based on information we've collected about our set of species - things like their physical features and the DNA sequences of their genes.

In a phylogenetic tree, the species or groups of interest are found at the tips of lines referred to as the tree's branches. For example, the phylogenetic tree below represents relationships between five species, A, B, C, D, and E, which are positioned at the ends of the branches:

The pattern in which the branches connect represents our understanding of how the species in the tree evolved from a series of common ancestors. Each branch point (also called an internal node) represents a divergence event, or splitting apart of a single group into two descendant groups.

At each branch point lies the most recent common ancestor of all the groups descended from that branch point. For instance, at the branch point giving rise to species A and B, we would find the most recent common ancestor of those two species. At the branch point right above the root of the tree, we would find the most recent common ancestor of all the species in the tree (A, B, C, D, E).

Each horizontal line in our tree represents a series of ancestors, leading up to the species at its end. For instance, the line leading up to species E represents the species' ancestors since it diverged from the other species in the tree. Similarly, the root represents a series of ancestors leading up to the most recent common ancestor of all the species in the tree.

Which species are more related?

In a phylogenetic tree, the relatedness of two species has a very specific meaning. Two species are more related if they have a more recent common ancestor, and less related if they have a less recent common ancestor.

We can use a pretty straightforward method to find the most recent common ancestor of any pair or group of species. In this method, we start at the branch ends carrying the two species of interest and "walk backwards" in the tree until we find the point where the species' lines converge.

For instance, suppose that we wanted to say whether A and B or B and C are more closely related. To do so, we would follow the lines of both pairs of species backward in the tree. Since A and B converge at a common ancestor first as we move backwards, and B only converges with C after its junction point with A, we can say that A and B are more related than B and C.

Importantly, there are some species whose relatedness we can't compare using this method. For instance, we can't say whether A and B are more closely related than C and D. That's because, by default, the horizontal axis of the tree doesn't represent time in a direct way. So, we can only compare the timing of branching events that occur on the same lineage (same direct line from the root of the tree), and not those that occur on different lineages.

Some tips for reading phylogenetic trees

You may see phylogenetic trees drawn in many different formats. Some are blocky, like the tree at left below. Others use diagonal lines, like the tree at right below. You may also see trees of either kind oriented vertically or flipped on their sides, as shown for the blocky tree.

The three trees above represent identical relationships among species A, B, C, D, and E. You may want to take a moment to convince yourself that this is really the case - that is, that no branching patterns or recent-ness of common ancestors are different between the two trees. The identical information in these different-looking trees reminds us that it's the branching pattern (and not the lengths of branches) that's meaningful in a typical tree.

Another critical point about these trees is that if you rotate the structures, using one of the branch points as a pivot, you don't change the relationships. So just like the two trees above, which show the same relationships even though they are formatted differently, all of the trees below show the same relationships among four species:

If you don't see right away how that is true (and I didn't, on first read!), just concentrate on the relationships and the branch points rather than on the ordering of species (W, X, Y, and Z) across the tops of the diagrams. That ordering actually doesn't give us useful information. Instead, it's the branch structure of each diagram that tells us what we need to understand the tree.

So far, all the trees we've looked at have had nice, clean branching patterns, with just two lineages (lines of descent) emerging from each branch point. However, you may see trees with a polytomy ( poly, many; tomy, cuts), meaning a branch point that has three or more different species coming off of it. In general, a polytomy shows where we don't have enough information to determine branching order.

If we later get more information about the species in a tree, we may be able to resolve a polytomy using the new information.

Where do these trees come from?

To generate a phylogenetic tree, scientists often compare and analyze many characteristics of the species or other groups involved. These characteristics can include external morphology (shape/appearance), internal anatomy, behaviors, biochemical pathways, DNA and protein sequences, and even the characteristics of fossils.

To build accurate, meaningful trees, biologists will often use many different characteristics (reducing the chances of any one imperfect piece of data leading to a wrong tree). Still, phylogenetic trees are hypotheses, not definitive answers, and they can only be as good as the data available when they're made. Trees are revised and updated over time as new data becomes available and can be added to the analysis. This is particularly true today, as DNA sequencing increases our ability to compare genes between species.

In the next article on building a tree, we'll see concrete examples of how different types of data are used to organize species into phylogenetic trees.

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Phylogenetic trees | Evolutionary tree (article) | Khan Academy

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Learn for free about math, art, computer programming, economics, physics, chemistry, biology, medicine, finance, history, and more. Khan Academy is a nonprofit with the mission of providing a free, world-class education for anyone, anywhere.

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Cell Structure (Julia Woods & Lila Ferreri)

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Cell Structure (Julia Woods & Lila Ferreri)

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This whole website is exciting and very interactive. You can explore the cell and all its organelles and features. This makes the connection because we have been studying the cell so much and all that it does.

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Ideas about cell structure have changed considerably over the years. Early biologists saw cells as simple membranous sacs containing fluid and a few floating particles. Today's biologists know that cells are infinitely more complex than this.

There are many different types, sizes, and shapes of cells in the body. For descriptive purposes, the concept of a "generalized cell" is introduced. It includes features from all cell types. A cell consists of three parts: the cell membrane, the nucleus, and, between the two, the cytoplasm. Within the cytoplasm lie intricate arrangements of fine fibers and hundreds or even thousands of miniscule but distinct structures called organelles.

Cell membrane

Every cell in the body is enclosed by a cell ( Plasma) membrane. The cell membrane separates the material outside the cell, extracellular, from the material inside the cell, intracellular. It maintains the integrity of a cell and controls passage of materials into and out of the cell. All materials within a cell must have access to the cell membrane (the cell's boundary) for the needed exchange.

The cell membrane is a double layer of phospholipid molecules. Proteins in the cell membrane provide structural support, form channels for passage of materials, act as receptor sites, function as carrier molecules, and provide identification markers.

Nucleus and Nucleolus

The nucleus, formed by a nuclear membrane around a fluid nucleoplasm, is the control center of the cell. Threads of chromatin in the nucleus contain deoxyribonucleic acid ( DNA), the genetic material of the cell. The nucleolus is a dense region of ribonucleic acid ( RNA) in the nucleus and is the site of ribosome formation. The nucleus determines how the cell will function, as well as the basic structure of that cell.

Cytoplasm

The cytoplasm is the gel-like fluid inside the cell. It is the medium for chemical reaction. It provides a platform upon which other organelles can operate within the cell. All of the functions for cell expansion, growth and replication are carried out in the cytoplasm of a cell. Within the cytoplasm, materials move by diffusion, a physical process that can work only for short distances.

Cytoplasmic organelles

Cytoplasmic organelles are "little organs" that are suspended in the cytoplasm of the cell. Each type of organelle has a definite structure and a specific role in the function of the cell. Examples of cytoplasmic organelles are mitochondrion, ribosomes, endoplasmic reticulum, golgi apparatus, and lysosomes.

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Ideas about cell structure have changed considerably over the years. Early biologists saw cells as simple membranous sacs containing fluid and a few floating particles. Today's biologists know that cells are infinitely more complex than this. There are many different types, sizes, and shapes of cells in the body.

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-In this article, it shows how DNA is located in nucleic acid

-It also shows the use of DNA in the nucleus

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Biological macromolecule
A large, organic molecule such as carbohydrates, lipids, proteins, and nucleic acids.

Monomer
A molecule that is a building block for larger molecules (polymers). For example, an amino acid acts as the building blocks for proteins.

Polymer
A large molecule made of repeating subunits (monomers). For example, a carbohydrate is a polymer that is made of repeating monosaccharides.

Types of biological macromolecules

Biological macromolecule

Building blocks

Functions

Examples

Carbohydrates

Monosaccharides (simple sugars)

Provide cells with quick/short-term energy, source of dietary fiber

Glucose, sucrose, starch, cellulose, chitin

Lipids

Fatty acids and glycerol

Provide cells with long-term energy, make up biological membranes

Fats, phospholipids, waxes, oils, grease, steroids

Proteins

Amino acids

Provide cell structure, send chemical signals, speed up chemical reactions, etc

Keratin (found in hair and nails), hormones, enzymes, antibodies

Nucleic acids

Nucleotides

Store and pass on genetic information

DNA, RNA

Common mistakes and misconceptions

Describing macromolecules as "large" is relative. We refer to them as "macro" because they are large compared to other, smaller molecules. However, this does not mean that they are large enough to view with the naked eye. Even a large protein, like hemoglobin, is still a million times smaller than a grain of rice!

Not all fats and carbohydrates are "bad." Information about different kinds of diets can be confusing and may lead someone to believe that all fats or all carbohydrates are unhealthy. This simply isn't the case. Fats and carbohydrates are actually essential for cellular function!

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Biological macromolecules review (article) | Khan Academy

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Learn for free about math, art, computer programming, economics, physics, chemistry, biology, medicine, finance, history, and more. Khan Academy is a nonprofit with the mission of providing a free, world-class education for anyone, anywhere.

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-This article talks about how DNA and our mitosis unit go hand in hand

- Both DNA replication and mitosis both happen in the cell cycle

-Mitosis happens after DNA replication because you need more extra DNA in the cell to create 2 new daughter cells

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Transcription occurs in one of the cell organelles called the nucleus

Translation occurs in the cell organelles called ribosomes

The different organelles help carry out the certain processes of DNA replication

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Cellular Structures and Processes Notes: Diagrams & Download PDF | Osmosis

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Cellular Structures and Processes High-Yield Notes by Osmosis. Detailed diagrams, vivid illustrations, and concise explanations.

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Cell Cycle Phases and Checkpoints- Allie Asche

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Cell Cycle Phases and Checkpoints- Allie Asche

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this article walks you through the cell cycle which was one of our units

as well as connect the process of DNA replication to the cell cycle

gives a great summary of most processes in the cell cycle

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Get the cell cycle definition and learn about its phases, checkpoints, and regulation. See which step is the longest.

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Why Is DNA Replication Such an Important Process?- Allie Asche

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Why Is DNA Replication Such an Important Process?- Allie Asche

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- the article talks about how DNA replication is a critical process that relates to our current unit

- the use of nucleotides(nucleic acids) is mentioned in this article which is a macromolecule, so those 2 units relate

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Why Is DNA Replication Such an Important Process?

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Explore the crucial role of DNA replication in maintaining genetic integrity and supporting cell reproduction through a detailed look at its mechanisms and enzymes.

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during the macromolecule unit we talked about Nucleic acids and DNA

In DNA replication it is a process to make amino acid chain and then proteins which is also one macromolecule we talked about

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Bioactivity and Biomedical Applications

Author links open overlay panel Amal Kumar Dhara ¹ , Amit Kumar Nayak ²

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Abstract

Biological macromolecules are large cellular components abundantly obtained naturally and are responsible for varieties of essential functions for the growth and survival of living organisms. There are four important classes of biological macromolecules, viz., carbohydrates, lipids, proteins, and nucleic acids. These possess some favorable characteristics, such as good biocompatibility, excellent biodegradability, desired mechanical strength, better bioavailability, etc., and these characteristics are directing the uses of these biological macromolecules in the biomedical and related fields. Biological macromolecules can also modulate the pathophysiology of neurodegenerative disorders/diseases. The current chapter deals with a brief discussion about the sources, properties, and valued applications of various biological macromolecules.

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Biological macromolecules are large cellular components abundantly obtained naturally and are responsible for varieties of essential functions for the...

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Viruses, climate change, and mRNA vaccines

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Viruses, climate change, and mRNA vaccines

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-We've talked about climate change and its potential effects on the exponentially growing human population

-One way this may occur is through an increase in virus spread and pandemics due to the spread of mosquitos and other virus-carrying organisms - warming environments allow them to spread to new places that were too cold in the past

-The COVID vaccine was developed so quickly through new technology that uses our body's own mRNA to make the protein from the virus (through translation!) and develop antibodies to that protein, so your immune system can easily recognize the virus and fight it off

-IN SUMMARY: mRNA vaccine technology offers a promising solution to the coming increase in pandemics caused by climate change

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Virus Spread Exacerbated by Modern Life, Climate Change

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Barbra Erickson, professor of anthropology, discusses how the new coronavirus (COVID-19) is an example of a “crowd disease” — the type that has only impacted humans since they began to live in dense populations.