CampbellActivity23answerkey - Activity 23.1 A Quick Review...

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Activity 23.1 A Quick Review of Hardy-Weinberg Population Genetics Part A. Review Chapter 23 of Biology, 7th edition. Then complete the discussion by filling in the missing information. If evolution can be defined as a change in gene (or more appropriately, allele) frequencies, is it conversely true that a population not undergoing evolution should maintain a stable gene frequency from generation to generation? This was the question that Hardy and Weinberg answered independently. 1. Definitions. Complete these definitions or ideas that are central to understanding the Hardy-Weinberg theorem. a. Population: An interbreeding group of individuals of the same species . b. Gene pool: All the alleles contained in the gametes of all the individuals in the population . c. Genetic drift: Evolution (defined as a change in allele frequencies) that occurs in small populations as a result of chance events. 2. The Hardy-Weinberg theorem. The Hardy-Weinberg theorem states that in a population that is not ( is/is not ) evolving, the allele frequencies and genotype frequencies remain constant from one generation to another. 3. Assumptions. The assumptions required for the theorem to be true are listed on page 449 of Biology, 6th edition, and are presented here in shortened form. a. The population is very large . b. There is no net migration of individuals into or out of the population. c. There is no net mutation ; that is, the forward and backward mutation rates for alleles are the same. For example, A goes to a as often as a goes to A d. Mating is at random for the trait/gene(s) in question. e. There is no selection . Offspring from all possible matings for the trait/gene are equally likely to survive.
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4. The Hardy-Weinberg proof. Consider a gene that has only two alleles, R (dominant) and r (recessive). The sum total of all R plus all r alleles equals all the alleles at this gene locus or 100% of all the alleles for that gene. Let p = the percentage or probability of all the R alleles in the population Let q = the percentage or probability of all the r alleles in the population If all R + all r alleles = 100% of all the alleles, then p + q = 1 (or p = 1 – q or q = 1 – p ) [ Note: Frequencies are stated as percentages (for example, 50%) and their associated probabilities are stated as decimal fractions (for example, 0.5).] Assume that 50% of the alleles for fur color in a population of mice are B (black) and 50% are b (brown). The fur color gene is autosomal. a.
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CampbellActivity23answerkey - Activity 23.1 A Quick Review...

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