Question 1

During which phase of meiosis does homologous recombination (crossing over) occur, and what is its evolutionary significance?

Accepted Answer

During prophase I; it increases genetic diversity by creating new allele combinations.

Question 2

A diploid cell (2n = 4) undergoes meiosis. After meiosis II, how many chromosomes and how much DNA (relative to the original cell) will each gamete contain?

Accepted Answer

2 chromosomes and 1x DNA

Question 3

Which of the following best explains why sexual reproduction leads to greater genetic variation than asexual reproduction?

Accepted Answer

Sexual reproduction involves homologous recombination, independent assortment, and random fertilization.

Question 4

According to the Law of Independent Assortment, what is the expected outcome when two genes are located on different chromosomes?

Accepted Answer

Each gene is inherited independently of the other.

Question 5

If a cell with genotype AaBb undergoes meiosis without crossing over, what are the possible gamete genotypes due to independent assortment?

Accepted Answer

AB, ab, Ab, aB

Question 6

Which event distinguishes meiosis I from mitosis?

Accepted Answer

Homologous chromosomes separate during meiosis I, but not during mitosis.

Question 7

A human cell in metaphase II of meiosis contains 23 chromosomes, each with two sister chromatids. What is the ploidy and DNA content relative to a gamete?

Accepted Answer

Haploid (1n), 2x DNA

Question 8

Which of the following is NOT a source of genetic variation in sexually reproducing organisms?

Accepted Answer

Binary fission

Question 9

In a Punnett square for a monohybrid cross (Aa x Aa), what do the letters on the margins represent?

Accepted Answer

The possible gametes produced by each parent

Question 10

Which process restores the diploid chromosome number in the life cycle of sexually reproducing organisms?

Accepted Answer

Fertilization

Question 11

A mutation occurs in a gene during DNA replication in a germ cell. Which of the following best describes the evolutionary significance of this event?

Accepted Answer

It introduces a new allele into the population, increasing genetic variation.

Question 12

Which of the following best describes the difference between homologous chromosomes and sister chromatids?

Accepted Answer

Homologous chromosomes are similar but not identical, while sister chromatids are identical copies.

Question 13

During which stage of meiosis do cells become haploid?

Accepted Answer

At the end of meiosis I cytokinesis

Question 14

Which of the following equations correctly represents the chromosome number change during fertilization in humans?

Accepted Answer

$$1n + 1n = 2n$$

Question 15

If a diploid organism has a genome with two chromosomes (one large, one small), how many genetically unique gametes can it produce due to independent assortment alone?

Accepted Answer

$$2^2 = 4$

Question 16

Which of the following best describes the outcome of crossing over during meiosis?

Accepted Answer

It produces recombinant chromatids with new allele combinations.

Question 17

Which of the following is true about the products of mitosis and meiosis in humans?

Accepted Answer

Mitosis produces two identical diploid cells; meiosis produces four unique haploid cells.

Question 18

Which of the following best explains why the chromosome number must be reduced during meiosis?

Accepted Answer

To maintain a constant chromosome number across generations after fertilization.

Question 19

Which of the following is a direct result of the random orientation of homologous chromosomes during metaphase I of meiosis?

Accepted Answer

Genetic variation among gametes due to independent assortment.

Question 20

A cell with genotype AaBb undergoes meiosis with crossing over between the A and B genes. Which of the following is a possible gamete genotype that would NOT be produced without crossing over?

Accepted Answer

A recombinant genotype such as Ab or aB

Inheritance and Sources of Genetic Variation: Meiosis, Mitosis, and Genetic Diversity

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