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The Outcome of Mutation [Internet]. Salt Lake City (UT): Genetic Science Learning Center; 2016 [cited 2019 Mar 10] Available from https://learn.genetics.utah.edu/content/basics/outcomes/

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Things You May Not Know About DNA [Internet]. Salt Lake City (UT): Genetic Science Learning Center; 2016 [cited 2018 Jan 19] Available from http://learn.genetics.utah.edu/content/basics/dnathings

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Genetic variation is important because when conditions change (food becomes scarce, environment changes), some individuals in a population will be more likely to have variations that will allow them to survive. Those who reproduce pass their genes to the next generation. Variation helps species survive, and it's the reason species change over time.

In asexual reproduction, variation comes mainly from mutation. Mutation is a natural process that introduces permanent changes in a DNA sequence. However, microbes also acquire genetic variation through transformation, transduction, and conjugation (gene transfer). These mechanisms often come into play when conditions are harsh.

In sexual reproduction, variation comes from both mutation and recombination. Mutation creates the different versions (or alleles) of the same gene. Parental alleles are then shuffled-or recombined-during meiosis. Because of recombination, sexual reproduction produces more variation than asexual does.

Most commonly, traits are influenced by multiple genes and the environment. So for most traits, patterns of inheritance are complex and unpredictable. For instance, when a sexually reproducing organism inherits a defective or "broken" allele that codes for a non-functional protein, the second copy can often make up for the loss. This type of interplay between alleles, especially when traits are influenced by multiple genes, makes predicting inheritance difficult, if not impossible.

A small number of traits are influenced primarily by a single gene. Traits influenced mainly by one gene usually have predictable patterns of inheritance. However, most of the time even supposed "single-gene" traits are influenced by multiple genes, as in the case of eye color. And often times, a single gene can influence multiple traits. For example, some genes involved in eye color also influence hair and skin color.

Why do so many textbooks pretend that eyes come in just two colors, brown and blue? Eye color is influenced by two major genes and several minor genes. Variations in these genes determine whether your eyes are brown, blue, green, gold, hazel, greyish-blue, brown with green flecks, blue with a gold ring...you get the idea.

In rare cases, changes in DNA sequences can cause disease. The pattern of disease inheritance can be predictable or unpredictable, depending on whether the disease is influenced mainly by one gene or by several genes. See Genetic Disorders

It's not quite accurate to say that everyone inherits two copies of every gene. In most mammals, the X and Y sex chromosomes determine whether an individual is male or female. Females have two X chromosomes, and therefore two copies of every gene. Males, however, have one X and one Y chromosome. For genes that appear only on the X chromosome or only on the Y (some do appear on both), males inherit just one copy.

Other living things have sex chromosomes too. Birds and reptiles have Z and W sex chromosomes. Unlike with X and Y, males have two Z chromosomes, and females have one Z and one W. Some insects and a few mammals have only an X chromosome. Females have two copies and males have one. However, sex is not always determined by chromosomes. With alligators, crocodiles, and most turtles, it's egg incubation temperature. And some fish can change gender in response to cues from the environment. Sex determination happens in many different ways.

Traits that involve genes on the sex chromosomes have different inheritance patterns than non-sex-linked traits. Color-blindness and Duchenne muscular dystrophy, for example, are linked to genes on the X chromosome. Both of these disorders are more common in males because they have just one X chromosome. They have no second allele to mask the effects of a defective gene.

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Genetic variation is important because when conditions change (food becomes scarce, environment changes), some individuals in a population will be more likely to have variations that will allow them to survive. Those who reproduce pass their genes to the next generation. Variation helps species survive, and it's the reason species change over time.

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Genes and Heredity - Science Lesson Plans - Genetics for Kids - Flocabulary

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Learn all about genes and heredity with Flocabulary's educational rap song and lesson plan.

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These models are based on the molecular structure of real nucleotides. The grey and white circles on the models represent partial positive and negative charges that form hydrogen bonds between complementary bases. These bonds work kind of like tiny magnets to hold the two DNA strands together.

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Mutation Generates New Alleles

The whole human family is one species with the same genes. Mutation creates slightly different versions of the same genes, called alleles. These small differences in DNA sequence make every individual unique. They account for the variation we see in human hair color, skin color, height, shape, behavior, and susceptibility to disease. Individuals in other species vary too, in both physical appearance and behavior.

Genetic variation is useful because it helps populations change over time. Variations that help an organism survive and reproduce are passed on to the next generation. Variations that hinder survival and reproduction are eliminated from the population. This process of natural selection can lead to significant changes in the appearance, behavior, or physiology of individuals in a population, in just a few generations.

Once new alleles arise, meiosis and sexual reproduction combine different alleles in new ways to increase genetic variation.

It's useful to think of mutation as a process that creates genetic variation. We often refer to a mutation as a thing-the genetic variation itself. This approach can be useful when it comes to a gene associated with a disease: the disease allele carries a mutation, a DNA change that compromises the protein's function. However, this approach gives mutation a bad name.

It's important to remember that losing the function of a gene doesn't always affect health. For example, most mammals have hundreds of genes that code for olfactory receptors, proteins that help us smell. Losing one of these genes probably doesn't make all that much difference.

In contrast to variations that cause disease, there are many more examples of variations that are neither good nor bad, but just different-like blood types and eye color. Just like with disease alleles, the process of mutation creates these more neutral variations. But with neutral variations, it can be impossible to tell which allele is the "normal" one that existed first and which is the "mutant"-and the distinction is often meaningless.

Mutation creates variations in protein-coding portions of genes that can affect the protein itself. But even more often, it creates variations in the "switches" that control when and where a protein is active and how much protein is made.

Lactase is an enzyme that helps infants break down lactose, a sugar in milk. Normally the gene that codes for lactase is active in babies and then turned off at about age four. When people who don't make lactase consume milk, they experience gas, nausea, and discomfort. But some people have a variation in a genetic switch that keeps the lactase gene active. This variation is called "lactase persistence," and people who have it can keep milk in their diets even as adults.

Other drivers of mutation: Environmental agents

Radiation, chemicals, byproducts of cellular metabolism, free radicals, ultraviolet rays from the sun-these agents damage thousands of nucleotides in each of our cells every day. They affect the nucleotides themselves: converting one base to another, knocking a base off its backbone, or even causing a break in the DNA strand.

Most of the time, mutation is reversed. DNA repair machines are constantly at work in our cells, fixing mismatched nucleotides and splicing broken DNA strands back together. Yet some DNA changes remain. If a cell accumulates too many changes-if its DNA is so damaged that repair machinery cannot fix it-it either stops dividing or it self-destructs. If any of these processes go wrong, the cell could become cancerous.

When we put on sun screen, we are protecting ourselves against mutation in somatic cells-the cells that make up the body and are not involved in reproduction.&ZeroWidthSpace; Only when DNA changes are carried in egg and sperm cells are they passed to the next generation. Believe it or not, a certain amount of sloppiness is built into the system. Without mutation there would be no variation, and without variation there would be no evolution.

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Mutation Generates New Alleles The whole human family is one species with the same genes. Mutation creates slightly different versions of the same genes, called alleles. These small differences in DNA sequence make every individual unique. They account for the variation we see in human hair color, skin color, height, shape, behavior, and susceptibility to disease.

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Identical twins have exactly the same DNA, but they are not exactly alike. Each twin has his or her own personality, talents, likes, and dislikes. There are even diseases that appear in one twin but not the other, including arthritis, diabetes, autism, schizophrenia, cancer, and many others. The differences between identical twins don't come from DNA-they all come from external factors.

Scientists often study twins to understand how genes and the environment work together to affect traits. They compare traits in identical twins, who have identical DNA, and fraternal twins, who share half their DNA, just like any siblings. If a characteristic appears more frequently in identical twin pairs than in fraternal twin pairs, then it has an inherited component.

The differences between identical twins don't come from DNA-they all come from external factors.

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Identical twins have exactly the same DNA, but they are not exactly alike. Each twin has his or her own personality, talents, likes, and dislikes. There are even diseases that appear in one twin but not the other, including arthritis, diabetes, autism, schizophrenia, cancer, and many others.

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The order of building blocks in a strand of DNA makes up a "sequence." We can read a DNA sequence like letters in a book. In fact, we know the sequence of the entire human genome-all 3 billion letters. That's enough information to fill roughly 1,000 200-page books!

Contained within the 3 billion letters of the human genome are about 21,000 genes. Most of our known genes code for proteins, but some code for RNA molecules.

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The order of building blocks in a strand of DNA makes up a "sequence." We can read a DNA sequence like letters in a book. In fact, we know the sequence of the entire human genome-all 3 billion letters. That's enough information to fill roughly 1,000 200-page books!

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Genetic Code, Crack Code, Nobel, Nirenberg, Educational, Game, Flash, DNA, RNA, Nobelprize.org, medicine, Nobel prize

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Kids learn about DNA and genes in the science of biology including the deoxyribonucleic acid molecule, nucleotides, codons, and interesting facts.

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A genetic disorder is a disease caused in whole or in part by a change in the DNA sequence away from the normal sequence. Genetic disorders can be caused by a mutation in one gene (monogenic disorder), by mutations in multiple genes (multifactorial inheritance disorder), by a combination of gene mutations and environmental factors, or by damage to chromosomes (changes in the number or structure of entire chromosomes, the structures that carry genes).

As we unlock the secrets of the human genome (the complete set of human genes), we are learning that nearly all diseases have a genetic component. Some diseases are caused by mutations that are inherited from the parents and are present in an individual at birth, like sickle cell disease. Other diseases are caused by acquired mutations in a gene or group of genes that occur during a person's life. Such mutations are not inherited from a parent, but occur either randomly or due to some environmental exposure (such as cigarette smoke). These include many cancers, as well as some forms of neurofibromatosis.

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A genetic disorder is a disease caused in whole or in part by a change in the DNA sequence away from the normal sequence. Genetic disorders can be caused by a mutation in one gene (monogenic disorder), by mutations in multiple genes (multifactorial inheritance disorder), by a combination of gene mutations and environmental factors, or by damage to chromosomes (changes in the number or structure of entire chromosomes, the structures that carry genes).

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NOVA Online | Cracking the Code of Life | Journey into DNA (non-Flash)

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Chances are you've seen an illustration of DNA's double-helix structure and even pictures of the chromosomes that make up the human genome. But where and how does the famous double helix fit into chromosomes, and how do chromosomes relate to the human body?

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Nobelprize.org, The Official Web Site of the Nobel Prize