Chapter 23: Test Your Understanding

There are 25 individuals in population 1, all with genotype AA, and there are 40 individuals in population 2, all with genotype aa. Assume that these populations are located far from each other and that their environmental conditions are similar. Based on the information given here, the observed genetic variation most likely resulted from a. genetic drift b. gene flow c. nonrandom mating d. directional selection

a. genetic drift

If the nucleotide variability of a locus equals 0%, what is the gene variability and number of alleles at that locus? a. gene variability = 0%; number of alleles = 0 b. gene variability = 0%; number of alleles = 1 c. gene variability = 0%; number of alleles = 2 d. gene variability > 0%; number of alleles = 2

b. gene variability = 0%; number of alleles = 1

A fruit fly population has a gene with two alleles, A1 and A2. Tests show that 70% of the gametes produced in the population contain the A1 allele. If the population is in Hardy-Weinberg equilibrium, what proportion of the flies carry both A1 and A2? a. 0.7 b. 0.49 c. 0.42 d. 0.21

c. 0.42

No two people are genetically identical, except for identical twins. The main source of genetic variation among humans is a. new mutations that occurred during the preceding generation b. genetic drift c. the reshuffling of alleles in sexual reproduction d. environmental effects

c. the reshuffling of alleles in sexual reproduction

Natural selection changes allele frequencies because some _______________ survive and reproduce better than others. a. alleles b. loci c. species d. individuals

d. individuals