BIOL202 - Study Guide - Lecture 20 - Population Genetics

BIOL202 - Study Guide - Lecture 20 - Population Genetics -...

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STUDY GUIDE: LECTURE 20 POPULATION GENETICS: EVOLUTION FROM A GENETICIST’S POINT OF VIEW READING: Red/Black Campbell 7 th ed. , pp 454-470. Green Campbell 6 th ed, pp. 446-454 Note: The textbook does a particularly nice job with this material. Many of the terms and questions below either come from the text or can be answered with help from the text. Also note: One of your laboratories, CHANGES IN THE ALLELE FREQUENCY IN A POPULATION OVER TIME , will be covered on this exam. The Introduction to that laboratory is also worth reading. TERMINOLOGY : genotype vs. phenotype of an individual organism : genotype determines phenotype gene vs. allele : gene flow : all the alleles entering or leaving the population gene pool : all the alleles that exist in the populations for a particular gene EQUATIONS (you will need to memorize these equations, know what terms stand for, and know how to use the equations to solve population genetics problems): p + q = 1 p 2 + 2pq + q 2 = 1 QUESTIONS: 1. a) How do “organismal” biologists, i.e., biologists that study phenotypic traits, define "evolution"? It is the change in the normal form of a population over the course of generations. b) How do geneticists define evolution? (use second definition in your overheads) A change in the relative frequencies of alleles in a population's gene pool over the course of generations.
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c) Explain why the difference in the two definitions is really just a matter of "focus." In other words, explain the relationship between a change in phenotype and the gene pool/allele frequencies. Phenotype is the morphological part to form. Since genotype is sometimes directly associated with phenotype, a change in genotype will result in a change in phenotype, or form. Vice versa, when there is a change in phenotype, that means that there has been a change in genotype; also a change in the gene pool/allele frequencies. 2. What is the basic "message" of the Hardy-Weinberg Theorem? (Don't memorize, explain it in your own words). Random mating/meiosis/sexual reproduction does not change freq of alleles. It tells us that as long as there is no migration and mutation, and there is natural selection, a large population, random mating and the population is in equilibrium, then the frequencies of the different genotypes in the population can be calculated. 3. What do population geneticists mean when they say that a population is in a “Hardy- Weinberg equilibrium" for the alleles of a particular gene (see overheads)? For example, say you had a population of mountain laurel bushes and, for a particular gene in this laurel population, there were four alleles: q1, q2, q3, q4. Say that the current allele frequencies were 34%, 42%, 20% and 4% for q1, q2, q3, q4, respectively. If the population is in "equilibrium" for these four alleles, what would that mean? The allele frequencies will remain the same generation after generation.
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This test prep was uploaded on 04/18/2008 for the course BIOL 202 taught by Professor Johnson during the Spring '05 term at Maryland.

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BIOL202 - Study Guide - Lecture 20 - Population Genetics -...

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