a. For each population, calculate the allele fre-
quencies and determine whether the pop-
ulation is currently at Hardy-Weinberg
equilibrium.
b. For populations not at Hardy-Weinberg equi-
librium, indicate whether there is an excess of
homozygous or heterozygous genotypes.
c. For populations not at Hardy-Weinberg
equilibrium, indicate how many generations
of random mating it would take for the pop-
ulation to reach equilibrium.- A sample of 100 individuals is genotyped at loci
A and B. The following numbers of two-locus
genotypes are obtained:
genotype^ number of individuals
A 1 A 1 B 1 B 1 36
A 1 A 2 B 1 B 2 48
A 2 A 2 B 2 B 2 16
a. What is surprising about the observed num-
ber of two-locus genotypes?
b. Determine whether each locus is at Hardy-
Weinberg equilibrium. What does your
answer tell you about this population?
c. Do you think the two loci are close to one
another, or far apart in the genome? - Cancers result from mutations in somatic cells,
and these mutations therefore are not passed
on to gametes. However, some families have
much higher rates of cancer than average,
showing that there are heritable factors that
contribute to the risk of developing cancer. Dis-
cuss the roles that somatic mutations and germ
line mutations play in producing cancer. - The Dscam locus in Drosophila melanogaster
has 24 exons. Four of these exons are able to
undergo alternative splicing. Exon 4 has 12 pos-
sible splice variants, exon 6 has 48 variants, exon
9 has 33 variants, and exon 17 has 2 variants. If all
splicing combinations are possible, how many
different Dscam protein sequences could be
encoded by a single allele at this locus?
04_EVOL4E_CH04.indd 101 3/23/17 8:55 AM