Genetics 303 | Biology homework help


Genetics 303

Fourth exam—take home 2019

Answer on SEPARATE paper, show all work, and be neat in the reporting of answers. It is easier to grade if you try to

keep the questions in sequence. STAPLE YOUR RESULTS!

1. In a human population, the genotype frequencies at one locus are 0.75 AA, 0.20 Aa, and 0.05 aa. What is the frequency

of the A allele [f(A)] and a allele [f(a)] for the population? Are they in Hardy-Weinberg equilibrium? (5 pts)

2. Calculate the number of heterozygotes in a population with p = 0.6 and q = 0.4 (at time = 0). After 4 generations of

inbreeding between siblings (F = 0.25) in a population of 650. (6 pts)

3. Human albinism is an autosomal recessive trait. Suppose that you find a village in the Andes where 8/1000 of the

population is albino. If the population size was 1600 and the population is in Hardy-Weinberg equilibrium with

respect to this trait, how many individuals are expected to be carriers (heterozygotes)? (5pts)

4. A boatload of 400 Swedish tourists, all of whom bear the MM blood group genotype, are marooned on Haldane Island,

where they are met by an population of Islanders totaling 1000, all bearing blood group NN genotype. In time, the

castaways become integrated into Island society. Assuming random mating, no mutation, no selection (based on

blood group), and no genetic drift, what would you expect the blood group distribution to be among 320 progeny of

the new Haldane Island population? (5 pts)

5. You identify a population of mice (Peromyscus maniculatus) on an island. Their coat color is controlled by a single

gene: BB mice are black, Bb mice are gray, and bb mice are white. You take a census of the population and record

the following numbers of mice:

Black 1156

Gray 408

White 36

(a) What are the frequencies of the two alleles? (4 pts)

(b) What are the Hardy-Weinberg equilibrium frequencies for these three phenotypes? (4 pts)

(c) A heat wave hits the island. All mice with black fur die from heat stroke, but the other mice survive. What are the new

allele frequencies for the population? (4 pts)

(d) If the population suffers no further cataclysms after the heat wave, and the surviving animals mate randomly, what will

be the frequency of mice with black fur in the next generation? (4 pts)

(e) If the climate is altered permanently, so that mice with black fur die before reproducing, which following statement is

correct? (5 pts)

(1) At Hardy-Weinberg equilibrium, f(B) will equal 0.135.

(2) The fitness of mice with gray fur (ωBb) must be equal to 0.5.

(3) The fitness of mice with black fur (ωBB) is 0.

(4) The B allele will disappear from the population in one generation.

(5) The B allele will disappear from the population in two generations.

6. Which of the following are requirements for evolution by natural selection? Explain your answer. (8 pts)

I Environmental change

II Differential survival and reproduction

III Heritability of phenotypic variation

IV Variation in phenotype

V Sexual reproduction



C) I, II, IV


E) II, IV, V

7. Which of the following processes is the source of genetic variation within populations? (8 pts)

A) Reproductive Isolation

B) Mutation

C) Selection

D) Asexual reproduction

E) Genetic drift

Explain your answer including a description of the impact of each on genetic variation.

8. If the population (17,377 in 2018) of folks in Perry, GA, had an f(a) = 0.2 and folks in Valdosta, GA, has a f(a) = 0.6,

then how many people from Valdosta, GA, would have to migrate to Perry to increase the population to

approximately f(a) = 0.3? (5 pts, remember, you can’t have fractional people)

9. What is the Ne of a population with the following annual censuses, [note: the drop in size due to 2010 and 2011 being

extreme drought years]? (5 pts)

2008: 9730

2009: 8810

2010: 3653

2011: 420

2012: 94

2013: 1560

2014: 5650

2015: 8700

2016: 9700

2017: 12110

2018: 15060

2019: 30789

10. Consider the following populations that have the genotypes shown in the following table:

Population AA Aa aa

1 1.0 0.0 0.0

2 0.0 1.0 0.0

3 0.25 0.50 0.25

4 0.25 0.25 0.50

5 0.333 0.333 0.333

6 0.0225 0.255 0.7225

7 0.5929 0.3542 0.0529

8 0.9604 0.0392 0.0004

a. What are p and q for each population? (4 pts)

b. Which of the populations are in Hardy-Weinberg equilibrium? (4 pts)

c. Populations 1 and 2 have a tree fall across their islands so that individuals can cross. If equal numbers of the

individuals occur on each island, what is the new population’s allele frequencies and genotype frequencies

after one generation of random mating? (6 pts)

d. In population 3, the a allele is less fit than the A allele, and the A allele is incompletely dominant. The result

is that AA is perfectly fit (= 1.0), Aa has a fitness of 0.8, and aa has a fitness of 0.6. With no mutation or

migration, graph the allele frequency of the a allele after 10 generations under selection (e.g., Time 0 = q

above, Time 1 = first generation after selection) (8 pts)

e. In population 8, the population size gets radically reduced to 50 individuals, total. What is the most likely

fate of the “a” allele, and what genetic principle would lead you to believe that the case? (4 pts)

11. You digest a linear piece of DNA with two restriction enzymes, BamH1 & Sma1, and get the following sized

fragments (in kb [kilobases]) (10 pts):

BamH1 Xho1 BamH1 & Xho1

10 kb 12 kb 8 kb

6 kb 8 kb 6 kb

4 kb 4 kb

2 kb

Draw the appropriate restriction fragment map based on this data labeling all restriction sites

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