Chapter 23

Natural selection changes allele frequencies because some survive and reproduce better than others. (A) alleles (B) loci (C) species (D) individuals

No two people are genetically identical, except for identical twins. The main source of genetic variation among humans is (A) new mutations that occurred in the preceding generation. (B) genetic drift. (C) the reshuffling of alleles in sexual reproduction. (D) environmental effects.

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 \(=2\)

A fruit fly population has a gene with two alleles, \(A 1\) and \(A 2\). Tests show that \(70 \%\) of the gametes produced in the population contain the \(A 1\) allele. If the population is in Hardy-Weinberg equilibrium, what proportion of the flies carry both \(A 1\) and \(A 2 ?\) (A) 0.7 (B) 0.49 (C) 0.42 (D) 0.21

EVOLUTION CONNECTION Using at least two examples, explain how the process of evolution is revealed by the imperfections of living organisms.