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AP®BiologyCollege BoardExam QuestionsUnit 5: HeredityMeiosis & Genetic Diversity

Meiosis & Genetic Diversity (College Board AP® Biology): Exam Questions

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Meiosis & Genetic Diversity

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1
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Which of the following best describes the role of meiosis in sexual reproduction?

  • It ensures that each gamete receives a haploid set of chromosomes, maintaining the chromosome number in offspring.

  • It produces identical daughter cells, ensuring that offspring are genetically identical to their parents.

  • It duplicates the chromosome number in each gamete, allowing for genetic variation.

  • It occurs in the zygote, leading to the development of an embryo.

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2
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A group of researchers is studying why siblings from the same parents do not look identical. They observed differences in traits such as eye color, hair type, and height.

Which process during meiosis is primarily responsible for generating genetic diversity in gametes?

  • DNA replication during the S phase of interphase.

  • Cytokinesis and formation of the nuclear membrane.

  • Crossing over between homologous chromosomes during meiosis I.

  • Random fertilization, where any sperm can fertilize any egg, leading to a unique combination of alleles in each offspring.

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A scientist examines a cell under a microscope and identifies homologous chromosomes aligning in the center of the cell. This alignment is an essential step in meiosis.

At which stage of meiosis do homologous chromosomes align at the metaphase plate before being separated?

  • Anaphase II

  • Metaphase II

  • Prophase I

  • Metaphase I

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A biologist is studying a species of butterfly that has 40 chromosomes in its somatic (body) cells. She needs to determine how many chromosomes are found in the gametes of the butterfly.

How many chromosomes are present in a single gamete of this butterfly?

  • 40

  • 20

  • 80

  • 10

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5
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A team of biologists is comparing mitosis and meiosis in a laboratory experiment using stained cells under a microscope. They observe that in both processes, chromosomes line up and segregate into new cells, but the final outcomes differ significantly.

Which of the following best describes a key similarity and a key difference between mitosis and meiosis?

  • Both processes result in identical daughter cells, but meiosis occurs in gametes while mitosis occurs in somatic cells.

  • Both processes involve chromosome segregation, but meiosis produces four genetically unique cells, while mitosis produces two identical cells.

  • Both processes produce the same number of daughter cells, but meiosis occurs in reproductive organs while mitosis occurs throughout the body.

  • Both processes involve two rounds of division, but meiosis occurs in all cells while mitosis is limited to specific tissues.

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In onion plants, Allium cepa, the diploid number is 16, meaning it has 8 homologous pairs of chromosomes.

After meiosis occurs, which of the following is the correct number of different chromosomal combinations that can result from independent assortment alone?

  • 256

  • 128

  •  65 536

  • 64

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2
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In an animal species, gametes are produced through meiosis. During metaphase I, homologous chromosomes align randomly along the spindle equator.

This random alignment results in which of the following?

  • crossing over

  • independent assortment

  •  mutation

  • genetic drift

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3
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In a laboratory, a researcher is studying meiosis in animal cells. She observes the chromosomes condensing and the nuclear envelope breaking down, with centrioles moving to opposite poles.

Which stage of meiosis is the researcher most likely observing?

  • prophase I

  • metaphase II

  • telophase I

  •  cytokinesis

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Figure 1 shows a specific stage of meiosis characterized by the arrangement of chromosomes.

Diagram illustrating a cell in metaphase with duplicated chromosomes separating, connected by spindles in an oval cell structure.
Figure 1. A cell moving through meiosis.

Which of the following statements is true regarding the events occurring during this stage of meiosis?

  • The centromeres of homologous chromosomes are pulled apart, leading to the separation of sister chromatids.

  • The genetic variability among the resulting gametes is influenced by the independent assortment of chromosomes during this stage.

  • DNA replication occurs to ensure each daughter cell receives an identical set of chromosomes.

  • Each chromosome consists of two non-identical sister chromatids due to prior crossing over.

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Scientists hypothesized that a group of genetically diverse marine organisms would show greater reproductive success in a rapidly changing environments than their genetically uniform relatives.

Which of the following best explains how meiosis could contribute to the evolutionary success of this population?

  • Meiosis results in genetically diverse offspring, increasing the chance that some individuals have advantageous traits in changing environments.

  • Meiosis allows offspring to inherit an exact copy of the parent genes, preserving favorable traits for future generations.

  • Meiosis eliminates harmful mutations, ensuring that only the strongest individuals survive.

  • Meiosis increases the speed of reproduction, allowing populations to expand rapidly in response to environmental change.

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In a population of flowering plants, researchers observed that flower color varies greatly between individuals. They hypothesized that the genetic diversity seen in the offspring was a result of both independent assortment and crossing over during meiosis. To test this hypothesis, they examined the offspring produced by crossing two heterozygous plants with different flower colors (Rr) and petal shapes (Tt). The table below shows the distribution of phenotypes from 200 offspring:

Phenotype

Number of offspring

red flowers, round petals

60

red flowers, oval petals

40

white flowers, round petals

50

white flowers, oval petals

50

Which of the following claims is best supported by the data?

  • Only independent assortment contributes to genetic diversity.

  • Only crossing over contributes to genetic diversity.

  • Both independent assortment and crossing over contribute to genetic diversity.

  • Neither independent assortment nor crossing over contribute to genetic diversity.

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The SMC1 gene codes for a protein that forms part of a cohesin complex. This complex is involved with holding DNA replicates together after S phase is completed.

A researcher studied a population of fruit flies in which a mutation in the SMC1 gene resulted in a high frequency of aneuploidy in gametes. Genetic analysis revealed that affected flies produced gametes with missing or extra chromosomes, leading to abnormal offspring with developmental defects.

Which of the following best explains how this mutation could cause aneuploidy?

  • The mutation causes early separation of sister chromatids, leading to incorrect segregation of chromosomes.

  • The mutation prevents DNA replication before meiosis, leading to an insufficient number of chromosomes available for segregation in gametes.

  • The mutation causes chromosomes to be unequally distributed during cytokinesis, leading to cells with variable DNA content after each division.

  • The mutation directly affects the separation of homologous pairs of chromosomes, increasing the genetic material allocated to some gametes.

    The mutation prevents homologous chromosomes from crossing over in prophase II, reducing genetic diversity and leading to aneuploidy.

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A population of marine snails inhabits a dynamic coastal environment where temperature, salinity, and predator populations fluctuate seasonally. The snails reproduce sexually. Over multiple generations, scientists analyzed the genetic variation and survival rates of these snails and compared them to those of a closely related species in the same habitat that reproduce asexually.

The results are shown in Figure 1 and Figure 2 below:

Graph showing survival rates of snail populations over generations; yellow line indicates sexual reproduction with higher survival, red line shows asexual.
Figure 1: Survival rates in two snail species over ten generations
Graph of genetic diversity over generations in snail populations. Yellow line shows sexual reproduction increases diversity; orange line for asexual remains stable.
Figure 2: Genetic diversity in two snail species over ten generations

Based on the data presented, which of the following provides the best explanation for the observed differences in genetic diversity and survival rates between the two populations?

  • Meiosis increases genetic diversity through recombination and random assortment, enhancing evolutionary fitness by allowing natural selection to favor adaptive traits.

  • Sexual reproduction means that offspring inherit a balanced mix of parental genes, preventing allele loss and maintaining evolutionary fitness.

  • Asexual populations lack meiosis, limiting beneficial mutations, while sexual populations eliminate harmful mutations, improving fitness over time.

  • Asexual organisms produce fewer offspring, reducing their ability to recover from environmental changes and lowering evolutionary fitness.

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A population of frogs is studied over 10 generations in an environment that experiences periodic flooding and droughts, leading to population bottlenecks at certain points. Researchers tracked heterozygosity levels (a measure of genetic variation) and found that although heterozygosity temporarily dropped in generations 4 and 8, it quickly recovered in subsequent generations.

The following data were collected:

Generation

Heterozygosity (%)

1

48

2

50

3

49

4

42 ⬇ (bottleneck)

5

52

6

53

7

54

8

47 ⬇ (bottleneck)

9

55

10

55

Based on the observed heterozygosity trends in the table, which of the following best explains how genetic diversity is maintained in this population despite periodic bottlenecks?

  • Random mating alone determines heterozygosity recovery after population declines.

  • Mutation rates increase after bottlenecks, introducing new alleles that drive heterozygosity back to pre-bottleneck levels.

  • Heterozygosity remains stable because meiosis produces identical gametes, ensuring beneficial alleles are preserved over time.

  • Crossing over and random assortment allow allele frequencies to recover in generations after bottleneck events.

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A researcher tracked nuclear DNA content per cell over time during two types of cell division. Figure 1 shows division type 1 and division type 2; different stages of cell division, X and Y, are labeled.

Graph showing relative mass of nuclear DNA per cell over time, in two division types. Peaks at 4 units (X), declines to 2 units (Y). Increasing steps pattern.
Figure 1: Mass of nuclear DNA over time

Which of the following correctly describes the observations made by the researcher?

  • After stage X in both division types 1 and 2, homologous chromosome pairs are preparing to undergo independent assortment.

  • During stage X in division type 1 the sister chromatids are aligned, allowing recombination to occur before chromosome separation.

  • After stage X in division type 2 the homologous chromosomes have been replicated and they pair together as tetrads, undergoing crossing over.

  • After stage Y the cells produced by division type 1 have the same number of chromosomes as those produced after the first stage Y in division type 2.

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