Population genetics and mendelian genetics...

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BIS 2B
Mendelian genetics practice questions 2014
1. You breed black labs. Labs exhibit epistasis for coat color. Dad is BbEe and mom is
BbEe, where B_ codes for black, and bb results in brown coat color. The E locus is
epistatic for coat color where ee pups are yellow. What colors are the parents? What is
the chance that a pup of the litter will be brown?
2. List the possible gamete genotypes produced by individuals of the following
genotypes. Start out by assuming that the A, B and C loci are unlinked.
a. Aa
b. AaBb
c. AAbbcc
d. AaBBCc
e. AaBbCc
List the possible genotypes that emerge from a test cross between an
individual of each of these genotypes with a homozygous recessive individual.
List all the possible phenotypes that could emerge from these test crosses if all
traits were strictly dominant? What are their frequencies?
List all the possible phenotypes that could emerge from these test crosses if all
traits were co-dominant? What are these frequencies?
3. You conduct a dihybrid cross of two parents that are both homozygous for both traits
to get an F1 generation where all individuals are heterozygous for both traits. Both traits
exhibit co-dominance.
You expect to observe how many different phenotypes in the F2 generation?
You expect to observe how many different genotypes in the F2 generation?
4. A mother with type A blood and a father with type B have children with type AB, type O
and type B. This pedigree can be explained by
A. Epistasis
B. Independent assortment
C. Pleiotropy
D. Segregation
E. Sex linkage
5. A flower color gene has two possible alleles (P, p). P is dominant to p, where PP and Pp are
purple and pp is white. Flower shape is referred to as Spurred (SS), partially spurred (Ss) and not
spurred (ss). The plant is self-compatible. The S and P loci are unlinked.
You start with a true breeding purple and spurred individual, and a true
breeding white and not spurred individual. You cross them. What kind(s) of
offspring do you get in the F1? What are the phenoptype(s) and genotype(s)?
Now you will cross the F1 offspring to get an F2 generation. What does the
Punnett Square that shows the possible outcomes of this cross look like?
How many different phenotypes can emerge from this cross?
What are the expected frequencies of phenotypes?
6. In peas, pink flower color depends upon anthocyanin synthesis. The C gene controls the
production of an anthocyanin precursor, and the P gene controls the conversion of that
precursor to anthocyanin. In plants homozygous for the recessive c allele at C, no
precursor is made, and therefore no anthocyanin pigment. In plants homozygous for the
recessive pp locus at P, precursor cannot be converted to anthocyanin pigment. Thus
unlinked.
If you make a cross between two CcPp heterozygote
parents, what will be the frequency of white-
flowered plants in the progeny? (Hint: the Punnett
square is your friend, but you may not need to fill in
all of the cells.)
A. 1/16
B. 3/16
C. 4/16
D. 7/16
E. 9/16
7. In progeny of a cross between genotypes AaBb and aabb, you observe the following
genotype frequencies: AaBb 6/16, Aabb 2/16, aaBb 2/16, aabb 6/16.
The best explanation for these results is
A. Epistasis
B. Independent assortment
C. Linkage
D. Pleiotropy
E. Segregation
19. A test cross between genotypes AaBb and aabb reveals the following gamete
frequencies: 25%AB, 25%Ab, 25%aB, 25%ab. An AaCc x aacc test cross reveals gamete
frequencies of 39% AB, 11% Ab, 9% aB, and 41% ab.
Which of the following is true?
A. A, B, and C are unlinked, and assort independently
B. A and C assort independently, but A and B are linked.
C. A, B, and C are linked, but A and C are closer together than A and B
D. A, B, and C are linked, but A and B are closer together than A and C
E. A and B assort independently, but A and C are linked
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Population genetics practice questions 2014 (Schmitt)
1. Given the following genotype frequencies, is each of these populations in Hardy-
Weinberg equilibrium? If not, determine which observed genotype frequencies > expected
and which observed genotype frequencies < expected.
A. AA = 0.01, Aa = 0.18, aa = 0.81
B. AA = 0.25, Aa = 0.50, aa = 0.25
C. AA = 0.36, Aa = 0.60, aa = 0.04
D. AA = 0.09, Aa = 0.42, aa = 0.49
E. AA = 0.64, Aa = 0.20, aa = 0.16
2. Which of the following phenomena is LEAST likely to cause changes in allele frequencies
over time within populations?
A. Assortative mating
B. Founder effects
C. Gene flow
D. Directional selection
E. Population bottlenecks
3. Rare deleterious recessive alleles are slow to be completely eliminated by natural
selection because
A. The fitness of homozygotes increases with declining allele frequency in the
population
B. Genetic drift becomes more important when the recessive allele is very rare.
C. When a recessive allele is rare, it occurs mostly in heterozygous individuals
where it does not affect relative fitness.
D. New mutations arise faster than natural selection can eliminate them from the
population.
E. Gene flow from other populations balances out the effects of natural selection.
4. Which of the following is NOT a possible mechanism for maintaining genetic variation
within populations?
A. Heterozygote advantage
B. Frequency-dependent selection
C. Gene flow
D. Population bottlenecks
E. Balancing selection
5. The most likely explanation for the frequent observation of multiple gametophytic self-
incompatibility alleles within plant populations is
A. Disruptive selection
B. Assortative mating
C. Gene flow
D. Epistasis
E. Negative frequency-dependent selection
6. Orange coat color in cats is caused by the X-linked codominant allele O. Suppose
that 20% of the male kittens in a feral population are orange. Assume that the
population is in Hardy-Weinberg equilibrium.
a. What is the frequency of the O allele in the population (2 points)?
b. Among females, what is
-- the predicted frequency of pure orange coats (2 points)?
-- the predicted frequency of calico (half orange) coats (2 points)?
7. You sample a population of butterflies at the end of the flying season, and score
them for their genotype for the enzyme PGI. In this population, there are two PGI
alleles: P1 and P2. You observe the following genotype frequencies: P1P1: 0.20
P1P2: 0.60, P2P2: 0.20
a. (2 points) What is the allele frequency for P1? ____ For P2?
b. 2 points) What is the expected frequency of each genotype under Hardy-
Weinberg equilibrium? P1P1:_______ P1P2 _________ P2P2
c. (4 points) Suggest two processes that could produce the observed pattern of
genotype frequencies
1
2
8. In a population exhibiting variation in two traits, where each trait has three
alleles, you measure allele frequencies of trait A to be: p = 0.2, q = 0.3, r =.5 and A3
(r) is recessive to A1(p) and A2 (q). For trait B, frequencies are, coincidentally, the
same as in A. Similarly B3 is recessive to B1 and B2. At Hardy Weinberg equilibrium
you predict that the population will contain what fraction of individuals that exhibit
both A3 and B3 recessive traits?
9. You use genetic sequencing to genotype a population of one of New Zealand
native mammals. You find that for the eye color allele (A is dominant for red eyes, a
is recessive for green eyes). However, there is an epistatic effect and a second locus
codes for eye pigment. The Allele for eye pigment (B) is dominant and at a
frequency of 0.6.The _____s that lack the eye pigment allele (bb) have yellow eyes.
What fraction of individuals do you expect to have yellow eyes?
Among just the individuals that have eye pigment (red or green), you
observe that 75% have red eyes and 25% of the population have green
eyes. Noticing historical notes of this species in the 1920s reporting the
same frequencies of eye color, you assume the population to be at Hardy-
Weinberg Equilibrium. What do you estimate to be the frequency of the A
allele in this population?
What is the expected frequency of Aa heterozygotes in the population?
What is the expected frequency of Aa heterozygotes among the yellow-
eyed individuals?
If both alleles are at Hardy Weinberg equilibrium, what proportion of the
entire population do you expect to have green eyes?
You discover a sub-population on an outlying island that has positive
assortative mating by eye color, but there remains no selective advantage
by eye color. Do you expect the frequency of individuals that are
heterozygous for red eyes to increase, decrease or have no effect?

 

Solution ID:350791 | This paper was updated on 26-Nov-2015

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