MB 21A

  1. The original source of all genetic variation is __________.

Mutation is, in itself, very important to evolution because it is the original source of the genetic variation that serves as the raw material for evolution.

  1. Of the choices listed below, which contributes the most to genetic variation among individuals in most prokaryote species?

In prokaryotes, which are haploid with a single allele for each gene, mutations immediately have their full effect. Since their generation times are very short, new mutations can proliferate rapidly.

  1. The smallest unit that can evolve is a _____.

population

Populations evolve as individuals with different genotypes live and die, causing changes in the gene pool.

  1. Members of the same population __________.

share a common gene pool

In studying evolution at the population level, biologists focus on the gene pool, which consists of all copies of every type of allele at every locus in all members of the population.

  1. Consider a hypothetical insect population of 100 individuals. Two equally represented alleles (A and a) exist for a particular gene. Which scenario is an example of microevolution in this population?

microevolution - the change in allele frequencies within a population over a relatively short period, often observable in real-time;The change in relative allele frequencies represents microevolution.

  1. Which condition would disturb the Hardy-Weinberg equilibrium and cause the gene pool to change?

Several homozygous recessive individuals leave the population.

Gene flow can alter allele frequencies in the population.

  1. If a population is in Hardy-Weinberg equilibrium and remains in equilibrium, which of the following will be true?

Hardy Weinberg Equilibrium - a principle in population genetics stating that allele and genotype frequencies remain constant across generations in the absence of evolutionary influences

Individuals survive and reproduce equally well regardless of their genotype.

Absence of selection is a condition of Hardy-Weinberg equilibrium.

  1. Suppose that, with regard to a particular gene with two alleles, A and a, we know that 60% of the alleles in the gene pool of a particular large population are A. We observe this population for five generations, during which we know that no mutation, selection, or migration has occurred. After this period, the frequency of the a allele is expected to be _____.

0.4

If 60% of the alleles are A, p = 0.6. Because q = 1 - p, the frequency of the a allele must be 0.4. The conditions are compatible with equilibrium, so those frequencies should be maintained.

  1. a) Which of the following are basic components of the Hardy–Weinberg model?

Frequencies of two alleles in a gene pool before and after many random matings

Hardy and Weinberg were trying to determine how and whether allele frequencies in a population change from one generation to the next.

  1. b) Which of the following statements is not a part of the Hardy–Weinberg principle?

The genotype frequencies in the offspring generation must add up to two.

This statement is not true; the genotype frequencies in the offspring generation must add up to one.

  1. c)

True or false? The Hardy–Weinberg model makes the following assumptions: no selection at the gene in question; no genetic drift; no gene flow; no mutation; random mating.

True

These are the five assumptions of the Hardy–Weinberg model.

  1. d) What is the frequency of the A1A2 genotype in a population composed of 20 A1A1 individuals, 80 A1A2 individuals, and 100 A2A2 individuals?

0.4

The calculation to determine the frequency of the A1A2 genotype is: 80 A1A2 individuals / (20 + 80 + 100) total individuals = 0.4, the frequency of the A1A2 genotype.

  1. e) What is the frequency of the A1 allele in a population composed of 20 A1A1 individuals, 80 A1A2 individuals, and 100 A2A2 individuals?

The frequency of the A1 allele is 0.3

The frequency of the A1 allele is p = (number of A1 alleles) / (total of all alleles) = [(2 ( 20) + 80] / [(2 × 20) + (2 × 80) + (2 × 100)] = 0.3.

  1. f) Which of the following evolutionary forces consistently results in adaptive changes in allele frequencies?

Selection

Selection is the only evolutionary force that consistently results in adaptation. Mutation without selection and genetic drift are random processes that may lead to adaptive, maladaptive, or neutral effects on populations.

  1. g) What genotype frequencies are expected under Hardy–Weinberg equilibrium for a population with allele frequencies of p = 0.8 and q = 0.2 for a particular gene?

The expected genotype frequencies are 0.64, 0.32, and 0.04 for A1A1, A1A2 , and A2A2 , respectively.

The expected frequency of the A1A1 genotype is p 2 = (0.8)(0.8) = 0.64; the expected frequency of the A1A2 genotype is 2pq = 2(0.8)(0.2) = 0.32; the expected frequency of the A2A2 genotype is q 2 = (0.2)(0.2) = 0.04. To verify your calculations, confirm that the three frequencies add up to one.

  1. h) Which of the following evolutionary forces could create new genetic information in a population?

mutation

Mutations, which are changes in a cell's DNA, can introduce new genetic information in a population.

  1. What is true of microevolution?

It is the kind of evolution that can change the relative abundance of a particular allele in a gene pool over the course of generations.        

Microevolution is a generation-to-generation change in allele frequency.