CHAPTER 15 Test Your Knowledge

Driving Question 1

By answering the questions below and studying Infographics 15.1 and 15.2, you should be able to generate an answer for the broader Driving Question above.

KNOW IT

Genetic diversity is measured in terms of allele frequencies (the relative proportions of specific alleles in a gene pool). A population of 3,200 mice has 4,200 dominant G alleles and 2,200 recessive g alleles. What is the frequency of g alleles in the population?

Of the three populations described below, each of which has 1,000 members, which population has the highest genetic diversity? Note that only one gene is presented, and that this gene has three possible alleles: A1, A2, and a. Population A: 70% have an A1/A1 genotype, 25% have an A1/A2 genotype, and 5% have an A1/a genotype.

Population B: 50% have an A1/A1 genotype, 20% have an A2/A2 genotype, 10% have an A1/A2 genotype, 10% have an A2/a genotype and 10% have an a/a genotype.

Population C: 80% have an A1/A1 genotype, and 20% have an A1/a genotype.

USE IT

A small population of 26 individuals has five alleles, A through E, for a particular gene. The E allele is represented only in one, homozygous individual:

Five individuals are D/A heterozygotes.

Five individuals are A/A homozygotes.

Five individuals are A/B heterozygotes.

Five individuals are C/D heterozygotes.

Five individuals are C/C homozygotes.

One individual is an E/E homozygote.

If five A/E heterozygotes migrate into the population, what will be the impact on the allele frequencies of each of the five alleles?

Some populations, for example cheetahs, have gene pools with very few different alleles. What approach(es) could be taken to try and introduce new alleles into these kinds of population?

From their gene pool and population size, which of the four populations in the accompanying table would you be most concerned about from a conservation perspective? Why would you be concerned?

The global human population continues to grow, and more people than ever are living in crowded cities. Given this situation, what selective pressures might the human population be currently facing or be expected to face in the near future?

Driving Question 2

By answering the questions below and studying Infographics 15.3, 15.4, and 15.5 and Table 5.1, you should be able to generate an answer for the broader Driving Question above.

KNOW IT

Which of the following are examples of genetic drift?

a. founder effect

b. bottleneck effect

c. inbreeding

d. a and b

e. a, b, and c

A bottleneck is best described as

a. an expansion of a population from a small group of founders.

b. a small number of individuals leaving a population.

c. a reduction in the size of an original population followed by an expansion in size as the surviving members reproduce.

d. the mixing and mingling of alleles by mating between members of different populations.

e. an example of natural selection.

A population of ants on a median strip has 12 different alleles, A through L, of a particular gene. A drunk driver plows across the median strip, destroying most of the median strip and 90% of the ants. The surviving ants are all homozygous for allele H. a. What is the impact of this event on the frequency of alleles A through L?

b. What type of event is this?

USE IT

Question 2 looked at the allele frequencies of three populations, A, B and C. From your answer to that question, which population would you predict to have the greatest chance of surviving an environmental change? Explain your answer.

In humans, founder effects may occur when a small group of founders immigrates to a new country, for example to establish a religious community. In this situation, why might the allele frequencies in succeeding generations remain similar to those of the founding population rather than gradually becoming more similar to the allele frequencies of the population of the country to which they immigrated?

Why is genetic drift considered to be a form of evolution? How does it differ from evolution by natural selection?

INTERPRETING DATA

The figure below shows a structure bar plot of moles from different parks in New York City. As in Infographic 15.2, each vertical bar represents genotypes from 18 genomic locations in one animal. The bars are color coded, with similar genotypes represented by the same color. From the data presented in the figure:

a. Are these three populations genetically isolated from one another? Explain your answer. What factors could explain their isolation, or lack thereof?

b. Is one of the populations potentially experiencing gene flow with another population? If so, which one, and how do you know?

Driving Question 3

By answering the questions below and studying Infographic 15.5 and Up Close: Calculating Hardy-Weinberg Equilibrium, you should be able to generate an answer for the broader Driving Question above.

KNOW IT

Which of the following statements is/are true about a nonevolving population?

a. Allele frequencies do not change over generations.

b. Genotype frequencies do not change over time.

c. Individuals choose mates with whom they share many alleles.

d. all of the above

e. a and b

A starting population of bacteria has two alleles of the TUB gene, T and t. The frequency of T is 0.8 and the frequency of t is 0.2. The local environment undergoes an elevated temperature for many generations of bacterial reproduction. After 50 generations of reproduction at the elevated temperature, the frequency of T is 0.4 and the frequency of t is 0.6. Has evolution occurred? Explain your answer.

Why is inbreeding detrimental to a population?

USE IT

Phenylketonuria (PKU) is a rare, recessive genetic condition that affects approximately 1 in 15,000 babies born in the United States. (You may have noticed on products that contain aspartame the statement “Phenylketonurics: contains phenylalanine,” a warning for people with PKU that they should avoid consuming that product.) Calculate the expected frequency of carriers (that is, of heterozygotes) in the U.S. population, based on the information provided about rates of PKU among U.S. births, assuming that the population is in Hardy-Weinberg equilibrium for this gene.

Assume a population of 100 individuals. Five are homozygous dominant (AA), 80 are heterozygous (Aa), and 15 are homozygous recessive (aa) for the A gene. Determine p and q for this gene for this population. Now use those values for p and q and plug them into the Hardy-Weinberg equation. Is this population in Hardy-Weinberg equilibrium? Why or why not?

Driving Question 4

By answering the questions below and studying Infographics 15.7 and 15.8, you should be able to generate an answer for the broader Driving Question above.

KNOW IT

The biological species concept defines a species

a. on the basis of similar physical appearance.

b. on the basis of close genetic relationships.

c. on the basis of similar levels of genetic diversity.

d. on the basis of the ability to mate and produce fertile offspring.

e. on the basis of recognizing one another’s mating behaviors.

How does geographic isolation contribute to speciation?

USE IT

Two populations of rodents have been physically separated by a large lake for many generations. The shore on one side of the lake is drier and has very different vegetation from that on the other side. The lake is drained by humans to irrigate crops, and now the rodent populations are reunited. How could you assess if they are still members of the same species?

If geographically dispersed groups of a given species all converge at a common location during breeding season, then return to their home sites to bear and rear their young, what might happen to the gene pools of the different groups over time?