Question 1

Which of the following best explains why meiosis is essential for sexual reproduction in diploid organisms?

Accepted Answer

Meiosis reduces the chromosome number by half, preventing chromosome doubling in each generation.

Question 2

A fruit fly (Drosophila melanogaster) has a diploid number of 8 chromosomes. How many different combinations of chromosomes can be produced in its gametes due to independent assortment alone?

Accepted Answer

$$2^4 = 16$

Question 3

During which phase of meiosis do homologous chromosomes separate, and what is the result for the daughter cells?

Accepted Answer

Anaphase I; daughter cells are haploid with chromosomes consisting of two sister chromatids.

Question 4

If a nondisjunction event occurs during meiosis II, what is the expected outcome for the resulting gametes?

Accepted Answer

Two gametes will be normal, one will have an extra chromosome (n+1), and one will be missing a chromosome (n-1).

Question 5

Which process during meiosis is primarily responsible for generating new combinations of alleles on the same chromosome?

Accepted Answer

Crossing over during prophase I

Question 6

A human zygote is found to have 47 chromosomes, including three copies of chromosome 21. Which meiotic error most likely caused this condition?

Accepted Answer

Nondisjunction during meiosis I or II in one parent, resulting in a gamete with two copies of chromosome 21

Question 7

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

Accepted Answer

Homologous chromosomes carry the same genes but may have different alleles; sister chromatids are identical copies of a single chromosome.

Question 8

If a diploid organism with a haploid number $$n = 6$$ undergoes meiosis, how many chromosomes will each gamete contain?

Accepted Answer

$$6$$

Question 9

Which of the following best explains why sexual reproduction can be advantageous in environments with rapidly evolving pathogens?

Accepted Answer

Sexual reproduction increases genetic diversity, allowing some offspring to survive new pathogen challenges.

Question 10

A researcher observes that a certain plant species is tetraploid. What does this indicate about its chromosome sets?

Accepted Answer

It has four sets of chromosomes in each cell.

Question 11

Which of the following scenarios would most likely result in aneuploidy in a human embryo?

Accepted Answer

A failure of homologous chromosomes to separate during meiosis I in the egg-producing parent.

Question 12

According to the purifying selection hypothesis, why might sexual reproduction be favored over asexual reproduction?

Accepted Answer

Sexual reproduction reduces the spread of deleterious alleles by producing some offspring without them.

Question 13

Which of the following best describes the outcome of meiosis II?

Accepted Answer

Four haploid cells, each with unreplicated chromosomes.

Question 14

If a species has a haploid number $$n = 5$$, how many genetically distinct gametes can be produced by independent assortment alone?

Accepted Answer

$$2^5 = 32$

Question 15

Which of the following events occurs during late prophase I of meiosis and is critical for genetic recombination?

Accepted Answer

Formation of chiasmata and crossing over between non-sister chromatids

Question 16

A population of roundworms exposed to a lethal bacterial pathogen showed an increased rate of outcrossing over generations. What does this observation support?

Accepted Answer

The changing-environment hypothesis

Question 17

Which of the following would most likely occur if homologous chromosomes failed to pair during meiosis I?

Accepted Answer

Reduction division would not occur properly, possibly resulting in gametes with abnormal chromosome numbers.

Question 18

Which of the following best describes the relationship between ploidy and the total number of chromosomes in a cell?

Accepted Answer

Ploidy is the number of sets of chromosomes; total chromosome number equals ploidy times the haploid number.

Question 19

Which of the following is a direct consequence of random fertilization in sexually reproducing organisms?

Accepted Answer

It increases the number of possible genetic combinations in offspring.

Question 20

Which of the following statements about mitosis and meiosis is correct?

Accepted Answer

Homologous chromosomes pair and undergo crossing over only in meiosis.

Meiosis: Mechanisms, Genetic Variation, and Evolutionary Significance

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