Multiple choice Chapter 21

Which statement about the beak size of finches on the island of Daphne Major during prolonged drought is true?

Each bird's survival was strongly influenced by the depth and strength of its beak as the drought persisted.

How can genetic variation at the whole gene level (gene variability) be quantified?

by the average percentage of loci that are heterozygous

Which process in sexual reproduction results in diversity at the nucleotide level?

chromosome crossover

In peas, a gene controls flower color such that R = purple and r = white. In an isolated pea patch, there are 36 purple-flowering plants and 64 white-flowering plants. Assuming Hardy-Weinberg equilibrium, what is the value of q for this population?

- 0.80

Phenylketonuria (PKU) is a birth defect that causes an amino acid called phenylalanine to build up in the body. The frequency of individuals born in a population with PKU is q 2. There is one PKU (q 2) birth per 10,000 births. The frequency of the recessive allele for PKU in this population is q = 0.01. The frequency of the dominant allele in this population is p = 1 −− q = 0.99. What is the frequency of carriers (2pq) in this population?

- 2%

In a population of 200 seagulls, dark brown feathers are dominant to having only white feathers. If 160 of the 200 seagulls have brown feathers, what is the frequency of seagulls that are homozygous dominant?

- 31%

If, on average, 46% of the loci in a species' gene pool are heterozygous, then the average homozygosity of the species should be

- 54%.

Which statement about variation is true?

- All new alleles are the result of nucleotide variability.

Whenever diploid populations are in Hardy-Weinberg equilibrium at a particular locus,

the allele's frequency should not change from one generation to the next, but its representation in homozygous and heterozygous genotypes may change.

Recent research investigating variation in human height have found that a variety of genes at different loci, as well as early nutrition, especially that of the mother during gestation (the period of time during development of a fetus) and childhood years, influence height. Given this information, which of the following is correct?

- Phenotypes are usually the result of a combination of genes as influenced by the environment.

How did Mendel's model of inheritance help explain Darwin's theory of natural selection?

- by proposing a mechanism of how organisms could transmit discrete, heritable units to offspring

Which of the following describes a mechanism for generating more genes?

- duplication

It is estimated by a wide body of scientists that in recent decades we have begun another mass extinction event on Earth. Amphibians in particular have been in decline, sometimes due to climate change, and they therefore provide a possible early sign of dramatic biodiversity change to come. With respect to climate change and natural selection acting upon a population of one species of frog in a tropical rain forest, mutations of DNA sequences of the frog genome that are inherited by offspring

- may have no effect at all, be beneficial, or be harmful.

When evolution occurred on the Galápagos Islands, the finch beaks

- varied in size across the population and sometimes conferred benefits in feeding, survivorship, and reproduction that were passed down to surviving offspring.

What is a population in biology?

- when a group of individuals of the same species live in the same area and interbreed

In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of the allele a is 0.3. What is the frequency of individuals that are homozygous for this allele?

0.09

The frequency of a disease is 30/1000. This is a disease that follows a dominant/recessive pattern of inheritance on one gene (where the only affected individuals are all homozygous recessive). What is the frequency of the disease genotype q2?

3%

In a population of 200 mice, brown fur is dominant to gray fur. If 120 of the 200 mice have brown fur, what is the frequency of mice that are heterozygous?

46%

Which of the following is correct about genetic variation?

It must be present in a population before natural selection can act upon the population.

Why don't similar genotypes always produce the same phenotype?

Phenotypes can vary depending upon environment

Imagine you predict a particular frequency for a genotype, based upon detailed knowledge of that genotype frequency in population "X" of a species. Then, using the Hardy-Weinberg model, you find that the observed genotype frequency in a different population, named "Y" of the same species, is not significantly different from what you predicted/expected based on population "X."Which of the following should you conclude?

The particular gene of interest is not undergoing any mechanisms of evolution.

The Hardy-Weinberg equation p2 + 2pq + q2 = 1 allows you to calculate

genotype frequencies.

In the formula for determining a population's genotype frequencies, the 2 in the term 2pq is necessary because

heterozygotes can come about in two ways based upon parental gametes.

In the formula for determining a population's genotype frequencies, the pq in the term 2pq is necessary because

heterozygotes have two alleles.

Which of the following consistently improves the degree to which organisms are well suited for life in their environment?

natural selection

When using the Hardy-Weinberg equilibrium model, we assume that

natural selection is not occurring.

A mutation that is neither harmful nor beneficial is termed a

silent mutation.

Please use the following information to answer the questions below.HIV's genome of RNA includes the code for reverse transcriptase (RT), an enzyme that acts early in infection to synthesize a DNA genome off an RNA template. The HIV genome also codes for protease (PR), an enzyme that acts later in infection by cutting long viral polyproteins into smaller, functional proteins. Both RT and PR represent potential targets for antiretroviral drugs. Drugs called nucleoside analogs (NA) act against RT, whereas drugs called protease inhibitors (PI) act against PR.Which of the following represents the treatment option most likely to avoid the production of drug-resistant HIV (assuming no drug interactions or side effects)?

using moderate doses of NA and two different PIs at the same time for several months