Deck 18: Population Genetics

Question 1

Suppose that you are a genetic counselor,and a couple seeks your advice about BHT tasting (people who can taste BHT in processed food are recessive homozygotes for the "taster" allele and nontasters are homozygous dominant or heterozygous for the "nontaster" allele).Both prospective parents are nontasters,but a careful analysis of the husband's pedigree reveals that he is a carrier of the taster allele.The two alleles are in Hardy-Weinberg equilibrium,and the proportion of BHT tasters in the population is 16 percent.What is the probability that the couple's first child will be a nontaster of BHT?

A)0.0
B)0.32
C)0.81
D)0.86
E)1.0

Answer 1

0.86

Question 2

Suppose that a population of 100 black-footed ferrets has an initial heterozygosity (H)of 0.5.How many generations will it take for this population to decline to a heterozygosity of 0.25?

A)1
B)34
C)68
D)100
E)138

Answer 2

E

Question 3

Given below are the genotypic frequencies for a single gene with two alleles for three different populations.

$\begin{array}{llll} &\underline{A A} & \underline{A a}& \underline{a a}\\\text { Population 1 } & 0.25 & 0.50 & 0.25 \\\text { Population 2 } & 0.35 & 0.56 & 0.09 \\\text { Population 3 } & 0.49 & 0.42 & 0.09\end{array}$

Which of the following is/are NOT correct about these three populations?

A)One must assume Hardy-Weinberg equilibrium to calculate the allele frequencies.
B)Only two of the populations are in Hardy-Weinberg equilibrium.
C)Population 1 is in Hardy-Weinberg equilibrium;the frequency of allele A is 0.5.
D)Population 2 is not in Hardy-Weinberg equilibrium;the frequency of allele a is 0.37.
E)Population 3 is in Hardy-Weinberg equilibrium;the frequency of allele a is 0.3.

Answer 3

One must assume Hardy-Weinberg equilibrium to calculate the allele frequencies.

Question 4

After a thorough analysis of the DNA from 150 university students,a small region of the human X chromosome is found to have three SNP sites.Two of those sites have three different variants,while the third site has four.How many different haplotypes were present in each student's cells?

A)1 or 2
B)3 or 6
C)10 or 20
D)32 or 64
E)It is impossible to determine based on this information alone.

Question 5

Which of the following is a question that population genetics would address?

A)How does cancer spread from one tissue to another?
B)How does the cell copy DNA?
C)How does a single nucleotide substitution cause sickle cell anemia?
D)How many people have colorblindness in Utah?
E)How does phenylketonuria affect brain development?

Question 6

Which of the following best describes the frequency of alleles in a Hardy-Weinberg population?

A)p²
B)q²
C)p + q
D)2pq
E)None of the answers options are correct.

Question 7

If 64% of the people in a population are blue-eyed and the population is in Hardy-Weinberg equilibrium,what is the percentage of heterozygotes in the population?

A)16%
B)20%
C)32%
D)36%
E)It is impossible to make an estimate from these data.

Question 8

A population is currently in Hardy-Weinberg equilibrium with respect to the A locus.If (positive)assortative mating occurs for one generation,the expected outcome is an increase in the frequency of the:

A)A allele.
B)a allele.
C)A^- phenotype.
D)heterozygous genotype (A/a).
E)homozygous genotypes (A/A and a/a).

Question 9

A gene or a trait is said to be polymorphic if:

A)the allele frequency is about 50:50 for each of its alleles present in the population.
B)the allele frequency of one allele is higher than that of all others.
C)more that one form (morph or allele)exists in the population.
D)one of its alleles occurs at a frequency lower than 1%.
E)only one form exists in the population.

Question 10

In a human population,the genotype frequencies at one locus are 0.5 AA,0.4 Aa,and 0.1 aa.The frequency of the A allele is:

A)0.20.
B)0.32.
C)0.50.
D)0.70.
E)0.90.

Question 11

You are studying an X-linked trait.There are two alleles,one showing complete dominance over the other.In females,84 percent show the dominant phenotype.What percentage of the males will show the dominant phenotype,assuming that individuals in this large population mate at random with respect to this trait?

A)84
B)60
C)40
D)36
E)16

Question 12

The genetic frequencies of two separate populations are: $$\begin{array} { | c c c c | } \hline & A A & A a & a a \\\hline \text { Population 1 } & .36 & .48 & .16 \\\text { Population 2 } & .33 & .33 & .33 \\\text { Popllation 3 } & .55 & .10 & .35 \\\hline\end{array}$$ Which of these populations are in Hardy-Weinberg equilibrium?

A)Population 1 is in Hardy-Weinberg equilibrium,but populations 2 and 3 are not.
B)Population 2 is in Hardy-Weinberg equilibrium,but populations 1 and 3 are not.
C)Population 3 is in Hardy-Weinberg equilibrium,but populations 1 and 2 are not.
D)Populations 1 and 2 are in Hardy-Weinberg equilibrium,but population 3 is not.
E)None of the populations are in Hardy-Weinberg equilibrium.

Question 13

Human albinism is an autosomal recessive trait.Suppose that you find a village in the Andes where one-fourth of the population is albino.If the population size is 1000 and the population is in Hardy-Weinberg equilibrium with respect to this trait,how many individuals are expected to be heterozygotes?

A)50
B)250
C)300
D)500
E)750

Question 14

In a tropical human population in Hardy-Weinberg equilibrium for an autosomal locus determining presence/absence of pigment in the skin,the frequency of albinism (aa)is 1 in 10,000.The frequency of heterozygotes is approximately:

A)1 in 25.
B)1 in 50.
C)1 in 75.
D)1 in 100.
E)1 in 1000.

Question 15

Inbreeding in populations that are normally outbreeding leads to which of the following?

A)a higher rate of genetic drift
B)a higher rate of mutation
C)an increase in the frequency of heterozygotes
D)more individuals affected by rare diseases
E)a smaller population

Question 16

Sequencing of a population of 110 dogs has revealed nine polymorphic sites within a small region of chromosome 11.All four possible variants were observed for each site.Based on these data,one can say that:

A)all the dogs in the sample population have different haplotypes.
B)different haplotypes have different frequencies in the sample population.
C)not all possible haplotypes are present in the sample population.
D)the sample population is not representative of the entire population.
E)some of the dogs in the sample population have the same haplotype.

Question 17

In a population of rats,35% of the individuals are genotypically B/B,10% are B/b,and 55% are b/b.Assuming there are no mutations,no selection and no migrations,the predicted frequency of the b/b genotype after one generation of random mating is:

A)25%.
B)42.25%.
C)47.5%.
D)55%.
E)57.5%.

Question 18

In a population in Hardy-Weinberg equilibrium,what will be the proportion of matings between homozygotes?

A)p² + 2pq
B)p⁴
C)p⁴ + q⁴
D)p⁴ + q⁴ + 2p²q²
E)4p2q²

Question 19

If the frequency of the recessive allele that causes phenylketonuria (PKU)when homozygote is about 0.01 in European and American populations,what is the estimated heterozygote frequency in these populations? (Assume that people mate randomly with respect to PKU,and that the mutant allele does not have any effects on fitness.)

A)about 0.0001
B)about 0.01
C)about 0.0198
D)about 0.99
E)It is impossible to make an estimate.

Question 20

Some forms of cleft palate are caused by recessive alleles of a gene on the X chromosome.In an Icelandic population,3.6 * 10^-3 of the females have this form of cleft palate.What proportion of the males would you expect to be affected,assuming Hardy-Weinberg equilibrium?

A)1.3 *10^-5
B)3.6 *10^-3
C)1.6 *^-3
D)6.0 *10^-2
E)0

Question 21

What is the probability that individual "A" in the pedigree below is homozygous by descent?

A)1/8
B)1/16
C)1/32
D)1/64
E)1/256

Question 22

If two populations of birds with frequencies of an allele a of 0.2 and 0.3 are forced together by unusually high winds,the new frequency of the a allele in the combined population will be:

A)0.2.
B)0.25.
C)0.3.
D)0.5.
E)It is impossible to determine unless we know the population sizes.

Question 23

Suppose that a population of 25 black-footed ferrets has an initial heterozygosity (H)of 0.5.How many generations will it take for this population to decline to a heterozygosity of 0.25?

A)1
B)34
C)68
D)100
E)138

Question 24

Which of the following conditions results in the faster evolution of a population?

A)mutation
B)selection
C)non-random mating
D)natural disaster

Question 25

Tay-Sachs disease is inherited as an autosomal recessive.In a certain large eastern European population,the frequency of Tay-Sachs disease is 1 percent.
a)If the population is assumed to be in Hardy-Weinberg equilibrium with respect to Tay-Sachs,what is the frequency of the allele that causes Tay-Sachs?
b)What would be the frequency of heterozygotes?
c)What is the probability of two heterozygotes marrying?
d)In children of such marriages,what would be the frequency of Tay-Sachs disease?
e)What proportion of all Tay-Sachs births are produced by such marriages?

Question 26

For many generations,the following genotypic frequencies were observed in a large population of dinosaurs: 4 % AA,32% Aa,and 64% aa.The climate changed abruptly and resulted in the death of all homozygous recessive dinosaurs (s = 1).In the next generation,the recessive homozygotes died shortly after birth.What percentage of these newborn dinosaurs died?

A)4%
B)8.5%
C)19.7%
D)36.8%
E)44%

Question 27

What is the inbreeding coefficient for individual "B" in the following pedigree?

A)1/8
B)1/16
C)1/32
D)1/64
E)1/256

Question 28

A recessive X-linked character appears in 40 percent of males and 16 percent of females in a randomly interbreeding population.Assume only two alleles are present.What are the allele frequencies? How many females are heterozygotes? How many males are heterozygotes?

Question 29

The table below shows the haplotypes relative to a small region on chromosome 2 for 10 strains of laboratory mice.All strains are homozygous with respect to the region in question.
$$\begin{array} { | l | l | l | l | l | l | l | } \hline \text { Strain } & \text { SNP1 } & \text { SNP2 } & \text { SNP3 } & \text { SNP4 } & \text { SNP5 } & \text { SNP6 } \\\hline + 1 & \text { A } & \text { G } & \text { G } & \text { T } & \text { A } & \text { C } \\\hline 2 & \text { A } & \text { T } & \text { C } & \text { T } & \text { G } & \text { C } \\\hline 3 & \text { A } & \text { G } & \text { C } & \text { T } & \text { A } & \text { C } \\\hline 4 & \text { A } & \text { G } & \text { C } & \text { T } & \text { A } & \text { C } \\\hline 5 & \text { T } & \text { G } & \text { C } & \text { G } & \text { A } & \text { C } \\\hline \text { 6 } & \text { A } & \text { T } & \text { C } & \text { T } & \text { A } & \text { T } \\\hline 7 & \text { A } & \text { G } & \text { A } & \text { T } & \text { A } & \text { T } \\\hline 8 & \text { T } & \text { G } & \text { C } & \text { G } & \text { G } & \text { C } \\\hline 9 & \text { A } & \text { C } & \text { C } & \text { T } & \text { A } & \text { G } \\\hline 10 & \text { A } & \text { G } & \text { T } & \text { A } & \text { A } & \text { G } \\\hline\end{array}$$
a)Based on the data in the table,what strains are genetically most closely related?
b)How many different haplotypes are represented in the table?
c)What SNP has the highest number of variants/alleles?

Question 30

How is the genetic composition of a population defined?

Question 31

Two chromosomes having the same combination of alleles at multiple loci are said to be of similar:

A)genotype.
B)haplotype.
C)phenotype.
D)sporotype.

Question 32

What group of organisms has,overall,the highest genetic diversity?

A)humans
B)invertebrates
C)plants
D)vertebrates other than humans
E)unicellular eukaryotes

Question 33

In a population,the D →d mutation rate is 4 *10^-6.If p = 0.8 today,what will p be after 50,000 generations?

A)0.1
B)0.25
C)0.65
D)0.8
E)None of the answer options are correct.

Question 34

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: $$\begin{array} { l l } \text { Black } & 200 \\\text { Gray } & 160 \\\text { White } & 40\end{array}$$
As a consequence of human activity,the climate on the island is changed permanently.All 200 mice with black fur die from heat stroke,but the other mice survive.If the climate change causes mice with black fur to die before reproducing,which of the following statements are correct?

A)The B allele will disappear from the population in one generation.
B)The B allele will disappear from the population in two generations.
C)The fitness of mice with gray fur (W_Bb)must be equal to 0.5.
D)The fitness of mice with black fur (W_BB)is 0.
E)At Hardy-Weinberg equilibrium,f(B)will equal 0.135.

Question 35

Red hair (autosomal recessive)is found in approximately 4 percent of the people in Norway.If we assume that the Norwegian population is in Hardy-Weinberg equilibrium with respect to hair color:
a)what are the frequencies of the red hair (r)and non-red hair (R)alleles?
b)what is the frequency of heterozygotes?
c)what proportion of all marriages could potentially have a child with red hair?

Question 36

In a population of rats,the relative fitness and frequencies of genotypes at present are: $$\begin{array} { l l l } & \text { Frequency } & \text { Fitness } \\H H & 0.4 & 1 \\H h & 0.5 & 0.8 \\h h & 0.1 & 0.6\end{array}$$
What will be the frequency of the h allele in the next generation?

A)0.3
B)0.4
C)0.5
D)0.6
E)0.7

Question 37

A boatload of Swedish tourists,all of whom bear the MM blood group,is marooned on Haldane Island,where they are met by an equally sized population of Islanders,all bearing blood group NN.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 4000 progeny of the new Haldane Island population?

A)4000 MN
B)2000 MN + 2000 MM
C)2000 MM + 2000 NN
D)2000 MN + 2000 NN
E)1000 MM + 2000 MN + 1000 NN

Question 38

Sequencing of a pine tree population reveals four variants of a particular SNP.Eighty percent (80%)of the trees have the G,15% the A,3% the T,and 2% the C variant.What is the genetic diversity of the pine tree population with respect to this SNP?

A)0.007%
B)2.0%
C)33.6%
D)66.4%
E)80%

Question 39

A horticulturist plans to self a plant,then (individually)self each of the F₁ plants,and repeat the same procedure until he obtains a plant that is heterozygous at no more than one gene.If the parental plant has 15,000 genes and is heterozygous for all of them,how many generations will this process take? (For the purposes of this question,count the parental plant as "1 generation.")

A)8 generations
B)15 generations
C)30 generations
D)15,000 generations
E)30,000 generations

Question 40

In a Pygmy group in central Africa,the frequencies of alleles determining the ABO blood groups were estimated as 0.2 for I^A,0.1 for I^B,and 0.7 for i.Assuming random mating with respect to blood group,determine the expected frequencies of the blood types A,B,AB,and O.

Question 41

Samples of brook trout from two mountain streams yielded the following data for a polymorphism for restriction fragment length (3.3-,3.9-,4.1-kilobases)at the gene encoding the enzyme alcohol dehydrogenase.


a)What are the allele frequencies in each population?
b)Are the populations at Hardy-Weinberg equilibrium?
c)What effect would migration of salmon from population 2 into the river where population 1 lives have on the allele frequencies in the progeny of population 1?

Question 42

What processes increase genetic variation in a given population?

Question 43

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.
$$\begin{array} { l l } \text { Black } & 200 \\\text { Gray } & 160 \\\text { White } & 40\end{array}$$
a)What are the frequencies of the two alleles?
b)What are the Hardy-Weinberg equilibrium frequencies for these three phenotypes?
c)A heat wave hits the island.All 200 mice with black fur die from heat stroke,but the other mice survive.What are the new allele frequencies for the population?
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?

Question 44

The table below shows the haplotypes relative to a small region on chromosome 2 for 10 strains of laboratory mice.All strains are homozygous with respect to the region in question.
What SNP shows the highest genetic diversity?
$$\begin{array} { | l | l | l | l | l | l | l | } \hline \text { Strain } & \text { SNP1 } & \text { SNP2 } & \text { SNPI } & \text { SNP4 } & \text { SNP5 } & \text { SNP6 } \\\hline 1 & \text { A } & \text { G } & \text { G } & \text { T } & \text { A } & \text { C } \\\hline 2 & \text { A } & \text { T } & \text { C } & \text { T } & \text { G } & \text { C } \\\hline 3 & \text { A } & \text { G } & \text { C } & \text { T } & \text { A } & \text { C } \\\hline 4 & \text { A } & \text { G } & \text { C } & \text { T } & \text { A } & \text { C } \\\hline5 & \text { T } & \text { G } & \text { C } & \text { G } & \text { A } & \text { C } \\\hline 6& \text { A } & \text { T } & \text { C } & \text { T } & \text { A } & \text { T } \\\hline 7 & \text { A } & \text { G } & \text { A } & \text { T } & \text { A } & \text { T } \\\hline8 & \text { T } & \text { G } & \text { C } & \text { G } & \text { G } & \text { C } \\\hline 9& \text { A } & \text { C } & \text { C } & \text { T } & \text { A } & \text { G } \\\hline 10& \text { A } & \text { G } & \text { T } & \text { A } & \text { A } & \text { G } \\\hline\end{array}$$

Question 45

The MN blood group in humans is under the control of a pair of codominant alleles,L^M and L^N.In a group of 556 individuals,the following genotypic frequencies are found:
$$\begin{array} { l l } 167 & M M \\280 & M N \\109 & N N\end{array}$$
a)Calculate the frequency of the L^M and L^N alleles.
b)Test (using the chi-squared test)whether the genotypic frequencies conform to the Hardy-Weinberg distribution.

Question 46

Apert syndrome (acrocephalosyndactyly)results from a dominant mutant allele.Among 322,182 births to normal parents,two infants were found with this syndrome.What is the mutation rate per gamete for this genetic disease?

Question 47

A population of lab rats recently escaped into the sewer system of Washington,D.C.A brave researcher sampled this population and estimated the following phenotypic frequencies,which were caused by a single gene with two alleles: E and e.
61% normal eyes(EE)
26% cross-eyed(Ee)
13% blind(ee)

a)If this population were to reach a Hardy-Weinberg equilibrium (HWE)in one generation,what would the phenotypic frequencies be in that new HWE generation?
b)Suppose that the phenotypes of the original adult population were not equally likely to survive and reproduce (selection).The fitness coefficients are as follows:
$$\mathrm { W } _ { E E } = 1 \quad \mathrm {~W} _ { Ee } = 0.6 \quad \mathrm {~W} _ { ee } = 0.2$$ What would be the expected phenotypic ratio of babies in the next generation (if selection acts only on adults)?

Question 48

A large population of hawkmoths lives in a valley in Canada.Genetic tests reveal the following frequencies of alleles for wing color.
$$\begin{array} { l l l } \text { Frequency } & \text { Allele } & \text { Phenotype } \\0.5 & C & \text { Black wing (dominarit to } c ^ { t } \text { and } c ^ { - } \text {) } \\0.4 & c ^ { t } & \text { Tan wing (dominarit to } c ^-) \\0.1 & c ^ { - } & \text {White wing (recessive to both other alleles) }\end{array}$$
a)If moths continue to mate randomly,what would be the frequencies of moths with black,tan,and white wings in the next generation?
b)A small group of the moths flies to neighboring Montana and starts a new population.After several generations,there is a large randomly-mating population of hawkmoths.Observations of the Montana moths reveal the following:
$$\begin{array} { l l } \text { Phenotype } & \text { Frequency } \\\hline \text { Black wings } & 0.75 \\\text { Tan wings } & 0 \\\text { White wirgs } & 0.25\end{array}$$ What are the allele frequencies for C,c^t,and c^-?
c)The change in allele frequency in the Montana population as compared with the original Canadian population is an example of _______.
d)A group of Western Kingbirds migrates into the area occupied by the Montana hawkmoths.The birds find it easier to spot and catch the white-winged moths,compared with the black moths.The relative fitness of each moth is as follows:
$$\begin{array} { l l } \text { Phenotype } & \text { Fitness } \\\text { Black wings } & 1 \\\text { White wings } & 0.2\end{array}$$ What will be the allele frequencies for C,c^t,and c^- after one generation of selection?
e)Imagine that instead of birds,hawkmoths from Idaho migrate into the Montana population.The Montana population contains 10,000 moths,and the migrants from Idaho number 2500.The Idaho moths are all white-winged.What is the allele frequency for c^- in the next generation?