Deck 21: Variation and Selection in Populations

Question 1

In 2013, a man was arrested for transporting 400 pounds of marijuana across state lines.His DNA was tested, entered into the CODIS database, and found to match the crime scene sample in a murder case (see Table).
$$\begin{array} { | l | c | c | } \hline & \text { Crime scene sample } & \text { Suspect 1 } \\\hline \text { SSR locus } 1 & 10,10 & 10,10 \\\hline \text { SSR locus } 2 & 11,11 & 11,11 \\\hline \text { SSR locus 3 } & 6,9 & 6,9 \\\hline\end{array}$$

-What additional evidence would increase your confidence that the man arrested for transporting marijuana committed the murder? (Select all that apply. )

A)A match between his blood and the crime scene sample at more than three SSR loci
B)A receipt that showed the man used his credit card in Texas on the night of the murder
C)The genotype at additional SSR loci that show a match at seven and a mismatch at three loci
D)Discovery of the man's fingerprints on the murder weapon

Answer 1

A match between his blood and the crime scene sample at more than three SSR loci
Discovery of the man's fingerprints on the murder weapon

Question 2

Why are many human recessive disease alleles maintained in populations despite continuing selection against them?

A)Heterozygotes have a higher fitness than either homozygote.
B)Mutations convert recessive alleles to dominant alleles.
C)Even when the allele frequency is low, many gametes contain the recessive allele.
D)Allele frequency remains constant from generation to generation.

Answer 2

A

Question 3

What is the term for the loss of genetic variation due to an event that decreases the size of the entire population?

A)gene flow
B)genetic drift
C)founder effect
D)population bottleneck
E)selection

Answer 3

D

Question 4

What evidence supports the hypothesis that humans originated in Africa?

A)H.sapiens genomes contain some alleles from Neanderthal genomes.
B)One Y chromosome lineage is that originated 1,000 years ago is found in 8% of modern day Asian men.
C)Alleles of nuclear genes are less variable in African populations than in other populations.
D)Mitochondrial DNA sequence variation is higher in African populations than in other populations.

Question 5

This population is in Hardy-Weinberg equilibrium.

Question 6

In 2013, a man was arrested for transporting 400 pounds of marijuana across state lines.His DNA was tested, entered into the CODIS database, and found to match the crime scene sample in a murder case (see Table).
$$\begin{array} { | l | c | c | } \hline & \text { Crime scene sample } & \text { Suspect 1 } \\\hline \text { SSR locus } 1 & 10,10 & 10,10 \\\hline \text { SSR locus } 2 & 11,11 & 11,11 \\\hline \text { SSR locus 3 } & 6,9 & 6,9 \\\hline\end{array}$$

-In a group of 100,000 people, about how many would be expected to have the same genotype as the crime scene sample? For simplicity, assume all SSR alleles are present in the population at a frequency of 0.2.

A)0.000256
B)6
C)13
D)51
E)None of the choices is correct.

Question 7

Brachydactyly is a condition caused by an allele dominant to wild-type in humans, in which the fingers and toes are shortened. In a population of 10,000 people, 1,600 are BB, 4,800 are Bb, and 3,600 are bb.

-What is the frequency of the b allele?

A)0.6
B)0.4
C)0.36
D)0.48
E)0.16

Question 8

Which of the following is one of the assumptions of the Hardy-Weinberg law?

A)The population is small.
B)Non-random mating occurs within the population.
C)Mutations appear in the gene pool at high frequency.
D)Migration occurs into or out of the population.
E)The ability of all genotypes to survive and reproduce is the same.

Question 9

In forensics, a DNA sample is analyzed to determine which alleles of 13 SSR loci are present.How is the probability of that specific combination of SSR alleles existing in the population calculated?

A)The frequency of each genotype is known from determining which allele is the rarest for each locus and then determining if the individual sample contains those alleles.
B)The total number of alleles for all loci in the population is calculated.
C)The Hardy-Weinberg Law is used to predict the genotype frequency at each locus.
D)The total number of alleles in the population is multiplied by 2.

Question 10

Brachydactyly is a condition caused by an allele dominant to wild-type in humans, in which the fingers and toes are shortened. In a population of 10,000 people, 1,600 are BB, 4,800 are Bb, and 3,600 are bb.

-What percentage of people in this population have short fingers and toes?

A)0%
B)16%
C)36%
D)64%
E)84%

Question 11

Why is the Hardy-Weinberg equation more accurate in predicting genotypic frequencies in the short run than in the long run?

A)The equation does not take epistasis into consideration.
B)The Hardy-Weinberg equation is based on Mendel's second law of inheritance.
C)The equation can be applied only to traits determined by single genes.
D)Populations do not conform to the assumptions of the Hardy-Weinberg law.

Question 12

What is the most common reason that new mutations are lost from a population?

A)Most mutations are caused by exposure to environmental mutagens that result in many mutations in the same individual, leading to death.
B)Most mutations are silent.
C)All new mutations result in lower reproductive fitness.
D)Populations are of a finite size and new mutations can be lost by chance.

Question 13

A large population of fish live in a lake. The color of their scales is determined by two different alleles of the S gene, S1 and S2. Homozygous S1 fish have yellow scales, S2 homozygotes have blue scales, and heterozygotes are green. Scientists catch 100 fish at random and record their color. Among those 100 fish are 30 yellow, 50 blue, and 20 green ones.

After the original sample is analyzed, an asteroid landed in the lake and killed all the fish that happened to be in one location. When 100 fish were sampled again, 15 were yellow, 75 were blue, and 10 were green.


-What is the frequency of the S¹ allele in the population before the asteroid hit?

A)0.15
B)0.40
C)0.50
D)0.60
E)0.80

Question 14

What has sequencing the genomes of modern humans, nonprimates, Neanderthals, and Denisovans determined about the relationship between modern humans and other lineages?

A)Denisovans and Neanderthals lived together in Europe about 30,000 years ago and interbred with each other.
B)The lineages leading to Denisovans, Neanderthals, and modern humans diverged 800,000 years ago and the different lineages did not exist at the same time.
C)Modern humans lived together with Neanderthals in Africa and interbred with them.
D)Modern humans are the direct descendants of Neanderthals.
E)Modern humans lived together and interbred with Denisovans in parts of Asia and the south Pacific.

Question 15

A large population of fish live in a lake. The color of their scales is determined by two different alleles of the S gene, S1 and S2. Homozygous S1 fish have yellow scales, S2 homozygotes have blue scales, and heterozygotes are green. Scientists catch 100 fish at random and record their color. Among those 100 fish are 30 yellow, 50 blue, and 20 green ones.

After the original sample is analyzed, an asteroid landed in the lake and killed all the fish that happened to be in one location. When 100 fish were sampled again, 15 were yellow, 75 were blue, and 10 were green.


-The fish population is in Hardy-Weinberg equilibrium before the asteroid hit.

Question 16

The proportion of individuals in a population that are of a particular genotype is the

A)phenotype frequency.
B)genotype frequency.
C)allele frequency.
D)None of the choices is correct.

Question 17

The sum total of all alleles carried in all members of a population is called the

A)gene pool.
B)genome.
C)ploidy.
D)polygenic sum.
E)polymorphism.

Question 18

The proportion of individuals in a population that are of a particular phenotype is the

A)phenotype frequency.
B)genotype frequency.
C)allele frequency.
D)None of the choices is correct.

Question 19

Why did the alleles that conferred insecticide resistance in mosquitoes become less frequent in the population when insecticide application was discontinued in the 1960s in Thailand?

A)The mosquitoes experienced a bottleneck and by chance the surviving insects had a low proportion of resistance alleles.
B)The resistance alleles were linked to a body color variation that led to resistant mosquitoes experiencing a higher rate of predation.
C)A mosquito population with a low proportion of resistant alleles migrated to Thailand and interbred with the original population.
D)In the absence of pesticide, mosquitos homozygous for the resistance alleles had lower fitness than the other genotypes.

Question 20

What does biological ancestry describe?

A)the ancestors from whom mitochondria were inherited
B)interaction between different generations in a population
C)the ancestors from whom specific alleles of nuclear genes were inherited
D)family trees or pedigrees

Question 21

In a population of 400 salamanders, some individuals have long toes and others have short toes.This phenotypic difference is due to a single gene with dominant and recessive alleles, T and t, where T confers long toes.If the toe length gene is in Hardy Weinberg equilibrium, and 256 individuals have short toes, how many individuals are heterozygous at the toe length locus?

A)More information is needed to determine the answer.
B)32
C)128
D)144

Question 22

A large population of fish live in a lake. The color of their scales is determined by two different alleles of the S gene, S1 and S2. Homozygous S1 fish have yellow scales, S2 homozygotes have blue scales, and heterozygotes are green. Scientists catch 100 fish at random and record their color. Among those 100 fish are 30 yellow, 50 blue, and 20 green ones.

After the original sample is analyzed, an asteroid landed in the lake and killed all the fish that happened to be in one location. When 100 fish were sampled again, 15 were yellow, 75 were blue, and 10 were green.


-What is the frequency of the S¹ allele in the fish population after the asteroid hit?

A)0.15
B)0.20
C)0.25
D)0.40
E)0.80

Question 23

Hardy-Weinberg conditions were established in the lake after the asteroid hit.The fish population mated and produced the next generation.Scientists sampled 100 fish that were all offspring of the post-asteroid population.How many yellow fish will be among the 100 offspring sampled?

A)4
B)8
C)15
D)30
E)32

Question 24

A large population of fish live in a lake. The color of their scales is determined by two different alleles of the S gene, S1 and S2. Homozygous S1 fish have yellow scales, S2 homozygotes have blue scales, and heterozygotes are green. Scientists catch 100 fish at random and record their color. Among those 100 fish are 30 yellow, 50 blue, and 20 green ones.

After the original sample is analyzed, an asteroid landed in the lake and killed all the fish that happened to be in one location. When 100 fish were sampled again, 15 were yellow, 75 were blue, and 10 were green.


-By what mechanism did allele frequencies change due to the asteroid?

A)Allele frequencies did not change because of the asteroid.
B)The asteroid caused mutations in the fish population.
C)The asteroid changed the environment, so fish with allele S² had increased fitness.
D)The asteroid killed fish because of their location, so the allele frequency changed by chance.