SUggESTIonS FoR FURTHER READIng
The chapter introduced some of the basic con-
cepts of population genetics that we will build
on in the next few chapters. A very good
introduction to this field is Principles of Popu-
lation Genetics by D. L. Hartl and A. g. Clark
(Sinauer, Sunderland, mA, 2007).
The large literature on mutation is nicely sum-
marized in a review by F. A. Kondrashov and
A. S. Kondrashov, “measurements of spon-
taneous rates of mutations in the recent past
and the near future” (Philos. Trans. Roy. Soc. B
365:1169–1176, 2010). P. D. Keightley’s “Rates
and fitness consequences of new mutations
in humans” (Genetics 190: 295–304, 2012)focuses on the rates and effects of new muta-
tions in humans. The interesting question of
how mutation rates evolve is explored by P. D.
Sniegowski and colleagues in “The evolution
of mutation rates: separating causes from con-
sequences” (Bioessays 22: 1057–1066, 2000)
and by m. Lynch in “Evolution of the mutation
rate” (Trends Genet. 26: 345–352, 2010).
The causes, consequences, and uses of linkage
disequilibrium in humans and other species
are reviewed by m. Slatkin in “Linkage dis-
equilibrium—understanding the evolutionary
past and mapping the medical future” (Nat.
Rev. Genet. 9: 477–485, 2008).PRoBLEmS AnD DISCUSSIon ToPICS
- Below are the DnA sequences that encode
the first eight amino acids for five alleles of the
Adh protein in Drosophila pseudoobscura.
nucleotides that differ from the first sequence
are shown by a lowercase letter.
ATgTCTCTCACCAACAAgAACgTC
ATggCTCTCACCAACAAgAACgTC
ATgTCgCTCACCAACAAgAACgTC
ATgTCTtTgACCAACAAgAACgTC
ATgTCTCTCACCAACAAgAACgTg
a. What are the first eight amino acids for each of
these five DnA sequences?
b. For each of the five polymorphic sites, indicate
whether the site represents a synonymous or
nonsynonymous polymorphism.
c. The fourth sequence shown above has two
mutational differences from the first sequence.
Specifically, the third codon is TTg versus CTC
in the first sequence. These two codons are
two mutational steps away from each other.
Supposing that the CTC sequence gave rise
to the TTg sequence, do you think it is more
likely that the one-difference intermediate
was TTC or CTg?
d. In general, synonymous polymorphisms tend
to be more common than nonsynonymous
polymorphisms. Why might that be?- The replica plate experiment shows that muta-
tions are random. However, certain environmen-
tal stresses (e.g., high temperature, high salt, low
pH) can increase the mutation rate.
a. Does this indicate that mutations are nonran-
dom, since they increase in response to cell
stressors?
b. Does increasing the mutation rate increase the
probability that an individual mutation will be
adaptive?
c. Does increasing the mutation rate increase the
probability that a cell will experience an adap-
tive mutation? - A species of daisy has hermaphroditic flowers
(i.e., each flower produces both male and female
gametes). Researchers genotyped 1000 individ-
uals at a SnP in three populations. The numbers
of each genotype in each population were:
genotype Population 1 Population 2 Population 3
TT 90 200 50
TC 420 200 500
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