Biology Chapter 15 and 23 - Quiz Questions

What is the frequency of the A1 allele in a population composed of 20 A1A1 individuals, 80 A1A2 individuals, and 100 A2A2 individuals?

.3

What is the frequency of the A1A2 genotype in a population composed of 20 A1A1 individuals, 80 A1A2 individuals, and 100 A2A2 individuals?

.4

Mutant tetraploid plants _____.

are unable to interbreed with a diploid plant

Homologous pairs of chromosomes are lined up independently of other such pairs during _____.

metaphase I

The original source of all genetic variation is _____.

mutation

Which of the following evolutionary forces could create new genetic information in a population?

mutation

What is the only evolutionary mechanism that consistently leads to adaptive evolution?

natural selection

Crossing over, resulting in an increase in genetic variation, occurs between _____.

nonsister chromatids of homologous chromosomes

The evolutionary effects of genetic drift are greatest when _____.

population size is small

According to the Hardy-Weinberg theorem, the frequencies of alleles in a population will remain constant if _____ is the only process that affects the gene pool.

sexual reproduction

how does diploidy help preserve genetic variation

t allows recessive alleles that may not be favored in the current environment to be preserved in the gene pool by propagation in heterozygotes

Genetic drift is a process based on _____.

the roll of chance

Mutation occurs when...

there is a change in the DNA sequence of a gene

True or false? The Hardy-Weinberg model makes the following assumptions: no selection at the gene in question; no genetic drift; no gene flow; no mutation; random mating.

true

Which syndrome is characterized by the XO chromosome abnormality?

turner syndrom

What name is given to the most common phenotype in a natural population?

wild type

what is a nondisjunction

An error in cell division that causes homologous chromosomes or sister chromatids to move to the same side of the dividing cell

A large population of laboratory animals has been allowed to breed randomly for a number of generations. After several generations, 25% of the animals display a recessive trait (aa), the same percentage as at the beginning of the breeding program. The rest of the animals show the dominant phenotype, with heterozygotes indistinguishable from the homozygous dominants. What proportion of the population is probably heterozygous (Aa) for this trait?

.5

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?

.8

In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of allele a is 0.1. What is the frequency of individuals with AA genotype?

.81

When can nondisjunction occur? Choose the best answer. 1 In meiosis, when homologous chromosomes fail to separate 2 All three answers are correct. 3 In mitosis, when sister chromatids fail to separate 4 In meiosis, when sister chromatids fail to separate

2

Which of the following evolutionary forces results in adaptive changes in allele frequencies? 1There is no evolutionary force that results in adaptive changes in allele frequencies. 2 Selection 3 Mutation 4 Nonrandom mating

2

Which of the following statements is not a part of the Hardy-Weinberg principle? 1 When alleles are transmitted according to the rules of Mendelian inheritance, their frequencies do not change over time. 2 The genotype frequencies in the offspring generation must add up to two. 3 Even if allele A1 is dominant to allele A2, it does not increase in frequency. 4 If allele frequencies in a population are given by p and q, then genotype frequencies will be given by p2, 2pq, and q2 for generation after generation.

2

In human gamete production there is an average of _____ crossover events per chromosome pair.

2-3

Which of the following are basic components of the Hardy-Weinberg model? 1 Allele frequencies, number of individuals in the population 2 Allele frequencies, phenotype frequencies 3 Frequencies of two alleles in a gene pool before and after many random matings 4 Allele frequencies in a subset of the population

3

Of the following chromosomal abnormalities, which type is most likely to be viable in humans? 1 Monosomy 2 Triploidy 3 Haploidy 4 Trisomy

4

What is true of microevolution? 1 It is evolution that involves only tiny changes to DNA, such as point mutations, producing only small (if any) changes to phenotype. 2 It is evolution that influences only a small subset of the populations that comprise a species. 3 It is evolution that is restricted to individual organisms. 4 It is the kind of evolution that can change the relative abundance of a particular allele in a gene pool over the course of generations. 5 It is evolution that results in the origin of small numbers of new species.

4

Which of the following is true of an X-linked gene, but not of a Y-linked gene? 1 It is expressed in half of the cells of either male or female. 2 It does not segregate like other genes. 3 It is only expressed in female offspring. 4 The gene is present in both males and females. 5 Sister chromatids separate during mitosis.

4

Which of the following results in a situation in which the chromosome number is either 2n+1 or 2n-1 ? 1.inversion 2 gene linkage 3 polyploidy 4 aneuploidy 5 methylation

4

Which of these terms applies to an organism with extra sets of chromosomes? 1 monosomy 2 haploid 3 trisomy 4 polyploid 5 diploid

4

A white-eyed female Drosophila is crossed with a red-eyed male Drosophila. Which statement below correctly describes the results? 1 Twenty-five percent of the females will have red eyes. 2 Twenty-five percent of the females will have white eyes. 3 None of the females will have red eyes. 4 Fifty percent of the females will have red eyes. 5 None of the females will have white eyes.

5

Hardy-Weinberg equilibrium must occur in populations wherein 1 an allele remains fixed. 2 no genetic variation exists. 3 natural selection is not operating. 4 All three of the responses above are correct. 5 Only two of the responses above are correct.

5

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

54%

If a diploid cell undergoes meiosis and produces two gametes with n + 1 chromosomes and two gametes with n− 1 chromosomes, what type of error occurred?

A nondisjunction error occurred in meiosis I, in which both members of a homologous pair migrated to the same pole of the cell.

If a diploid cell undergoes meiosis and produces two gametes that are normal, and one with n − 1 chromosomes, and one with n + 1 chromosomes, what type of error occurred?

A nondisjunction error occurred in meiosis II, in which both sister chromatids of a chromosome migrated to the same pole of the cell.

What genotype frequencies are expected under Hardy-Weinberg equilibrium for a population with allele frequencies of p = 0.8 and q = 0.2 for a particular gene?

The expected genotype frequencies are 0.64, 0.32, and 0.04 for A1A1, A1A2, and A2A2, respectively.

Rabbit ear size tends to decrease as latitude increases. This is an example of _____.

a cline

Every few years a giant axe chops off the head of every person who is over 6 feet tall. How will this affect the human population?

allels that promote "tallness" will decrease in frequency

What results if a fragment of a chromosome breaks off and then reattaches to the original chromosome at the same place but in the reverse direction?

an inversion

In evolutionary terms, an organism's fitness is measured by its _____.

contribution to the gene pool of the next generation

Blue poppies native to China were grown at a plant-breeding center in California. The plants with the thickest leaves were most likely to survive and reproduce in the drier climate. After several generations, the percentage of thick-leaved plants had increased by 42%. This adaptation of the poppies to their new environment is due to _____.

directional selection

What situation most likely explains the occasional high frequency of certain inherited disorders among human populations established by a small population?

founder effect

How are human mitochondria inherited?

from the mother only

The ease with which humans travel across the globe is likely to increase _____.

gene flow

Modern travel along with migration reduces the probability of _____ having an effect on the evolution of humans.

genetic drift

What phenomenon occurs when a particular allele will either be expressed or silenced, depending on whether it is inherited from a male or a female?

genomic imprinting

What can we observe in order to visualize Mendel's Law of Segregation?

homologous chromosomes separating during meiosis I

In general, the frequency with which crossing over occurs between two linked genes depends on what?

how far apart they are on the chromosome

Most polyploid plants arise as a result of _____.

hybridization