Evolution, 4th Edition

(Amelia) #1
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.


  1. 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?

  2. 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.

  3. 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

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