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Page 60

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How does PCR work? The polymerase chain reaction explained

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PCR is the central DNA technology. Scientists use PCR to diagnose disease, to modify genes, and everything in between. PCR is a conceptually simple yet tremendously powerful technique. This simple animation will help you understand how PCR can make millions of copies of any specific piece of DNA.

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Genes Meet the Environment Page 53

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Article Summarizing Charles Darwin's main points

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Article Summarizing Charles Darwin's main points

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Page 40 "Everything Evolves"

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Darwin's Theory of Evolution is the widely held notion that all life is related and has descended from a common ancestor: the birds and the bananas, the fishes and the flowers -- all related. Darwin's general theory presumes the development of life from non-life and stresses a purely naturalistic (undirected) "descent with modification". That is, complex creatures evolve from more simplistic ancestors naturally over time. In a nutshell, as random genetic mutations occur within an organism's genetic code, the beneficial mutations are preserved because they aid survival -- a process known as "natural selection." These beneficial mutations are passed on to the next generation. Over time, beneficial mutations accumulate and the result is an entirely different organism (not just a variation of the original, but an entirely different creature).

Darwin's Theory of Evolution - Natural Selection
While Darwin's Theory of Evolution is a relatively young archetype, the evolutionary worldview itself is as old as antiquity. Ancient Greek philosophers such as Anaximander postulated the development of life from non-life and the evolutionary descent of man from animal. Charles Darwin simply brought something new to the old philosophy -- a plausible mechanism called "natural selection." Natural selection acts to preserve and accumulate minor advantageous genetic mutations. Suppose a member of a species developed a functional advantage (it grew wings and learned to fly). Its offspring would inherit that advantage and pass it on to their offspring. The inferior (disadvantaged) members of the same species would gradually die out, leaving only the superior (advantaged) members of the species. Natural selection is the preservation of a functional advantage that enables a species to compete better in the wild. Natural selection is the naturalistic equivalent to domestic breeding. Over the centuries, human breeders have produced dramatic changes in domestic animal populations by selecting individuals to breed. Breeders eliminate undesirable traits gradually over time. Similarly, natural selection eliminates inferior species gradually over time.

Darwin's Theory of Evolution - Slowly But Surely...
Darwin's Theory of Evolution is a slow gradual process. Darwin wrote, "...Natural selection acts only by taking advantage of slight successive variations; she can never take a great and sudden leap, but must advance by short and sure, though slow steps." [1] Thus, Darwin conceded that, "If it could be demonstrated that any complex organ existed, which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down." [2] Such a complex organ would be known as an "irreducibly complex system". An irreducibly complex system is one composed of multiple parts, all of which are necessary for the system to function. If even one part is missing, the entire system will fail to function. Every individual part is integral. [3] Thus, such a system could not have evolved slowly, piece by piece. The common mousetrap is an everyday non-biological example of irreducible complexity. It is composed of five basic parts: a catch (to hold the bait), a powerful spring, a thin rod called "the hammer," a holding bar to secure the hammer in place, and a platform to mount the trap. If any one of these parts is missing, the mechanism will not work. Each individual part is integral. The mousetrap is irreducibly complex. [4]

Darwin's Theory of Evolution - A Theory In Crisis
Darwin's Theory of Evolution is a theory in crisis in light of the tremendous advances we've made in molecular biology, biochemistry and genetics over the past fifty years. We now know that there are in fact tens of thousands of irreducibly complex systems on the cellular level. Specified complexity pervades the microscopic biological world. Molecular biologist Michael Denton wrote, "Although the tiniest bacterial cells are incredibly small, weighing less than 10⁻¹² grams, each is in effect a veritable micro-miniaturized factory containing thousands of exquisitely designed pieces of intricate molecular machinery, made up altogether of one hundred thousand million atoms, far more complicated than any machinery built by man and absolutely without parallel in the non-living world." [5]

And we don't need a microscope to observe irreducible complexity. The eye, the ear and the heart are all examples of irreducible complexity, though they were not recognized as such in Darwin's day. Nevertheless, Darwin confessed, "To suppose that the eye with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest degree." [6]

Explore More Now!

1. Charles Darwin, "On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life," 1859, p. 162.

2. Ibid. p. 158.

3. Michael Behe, "Darwin's Black Box," 1996.

4. "Unlocking the Mystery of Life," documentary by Illustra Media, 2002.

5. Michael Denton, "Evolution: A Theory in Crisis," 1986, p. 250.

6. Charles Darwin, "On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life," 1859, p. 155.

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Darwin's Theory of Evolution is the widely held notion that all life is related and has descended from a common ancestor: the birds and the bananas, the fishes and the flowers -- all related. Darwin's general theory presumes the development of life from non-life and stresses a purely naturalistic (undirected) "descent with modification".

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Selective Study Page 42

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However, studies of these related viral lineages showed something surprising: primates with SIV and wild cats with FIV don't seem to be harmed by the viruses they carry. If scientists can figure out how non-human primates and wild cats are able to live with these viruses, they may learn how to better treat HIV infections or prevent them altogether.

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Page 43 "Clues from Variation"

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Mutation and Haplotypes [Internet]. Salt Lake City (UT): Genetic Science Learning Center; 2016 [cited 2019 May 23] Available from https://learn.genetics.utah.edu/content/basics/haplotype

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Living Laboratories Page 46

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A model organism is a species that has been widely studied, usually because it is easy to maintain and breed in a laboratory setting and has particular experimental advantages.

Model organisms are non-human species that are used in the laboratory to help scientists understand biological processes.

They are usually organisms that are easy to maintain and breed in a laboratory setting.

For example, they may have particularly robust embryos that are easily studied and manipulated in the lab, this is useful for scientists studying development.

Or they may occupy a pivotal position in the evolutionary tree, this is useful for scientists studying evolution.

Why are model organisms useful in genetics research?

Many model organisms can breed in large numbers.

Some have a very short generation time, which is the time between being born and being able to reproduce, so several generations can be followed at once

Mutants allow scientists to study certain characteristics or diseases. These are model organisms that have undergone a change or mutation in their DNA that may result in a change in a certain characteristic.

Some model organisms have similar genes or similar-sized genomes to humans.

Model organisms can be used to create highly detailed genetic maps:

Genetic maps are a visual representation of the location of different genes on a chromosome, a bit like a real map but one where the key landmarks are areas of interest in the genome.

For example, areas of DNA that differ between individuals in the same species (SNPs) or genes.

Examples of model organisms used to study genetics

Yeast (Saccharomyces cerevisiae)

Fruit fly (Drosophila melanogaster)

Nematode worm (Caenorhabditis elegans)

Western clawed frog (Xenopus tropicalis)

Mouse (Mus musculus)

Zebrafish (Danio rerio)

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A model organism is a species that has been widely studied, usually because it is easy to maintain and breed in a laboratory setting and has particular experimental advantages. Model organisms are non-human species that are used in the laboratory to help scientists understand biological processes.

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Relates to Page 52 "The Genome Zoo"

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NOVA Evolution Lab Game

Create phylogenetic trees and explore genetic relationships between species with NOVA's Evolution Lab. What could you possibly have in common with a mushroom, or a dinosaur, or even a bacterium? More than you might think. In this Lab, evaluate similarities in the traits and DNA of species, and conduct your own investigations in an open-ended interactive tree of life. Along the way, watch short animated videos that explain the evidence for evolution and illustrate it with specific examples. Come climb around the tree of life and see evolution-what some have called the greatest show on Earth-in action.

Find out more at the NOVA Evolution Lab.

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Create phylogenetic trees and explore genetic relationships between species with NOVA's Evolution Lab. What could you possibly have in common with a mushroom, or a dinosaur, or even a bacterium? More than you might think. In this Lab, evaluate similarities in the traits and DNA of species, and conduct your own investigations in an open-ended interactive tree of life.

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Genetics and You: You've Got Rhythm! Page 56

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Supplemental Resources on the Human Genome Project (timeline, overview, news reports, etc.)

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Supplemental Resources on the Human Genome Project (timeline, overview, news reports, etc.)

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Animals Helping People Page 58

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National Human Genome Research Institute (NHGRI)

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introduction to the human genome project

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All About The Human Genome Project (HGP)

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Introduction to the Human Genome Project, published by the National Human Genome Research Institute. This brief overview is aimed at students, teachers and other non-scientists.

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Page 58 My Collaborator is a Computer

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What is bioinformatics? A proposed definition and overview of the field. - PubMed - NCBI