Question 1

Which of the following best explains why meiosis is referred to as a 'lessening act'?

Accepted Answer

It reduces the chromosome number by half in gametes, ensuring that fertilization restores the diploid number.

Question 2

During which phase of meiosis does crossing over occur, and what is its genetic significance?

Accepted Answer

Crossing over occurs during prophase I and increases genetic variation by exchanging alleles between homologous chromosomes.

Question 3

If a diploid organism has a chromosome number of $$2n = 8$$, how many chromosomes will each gamete contain after meiosis?

Accepted Answer

$$n = 4$$

Question 4

Which process is responsible for the random distribution of maternal and paternal chromosomes to gametes?

Accepted Answer

Independent assortment

Question 5

A karyotype of a human cell shows 22 pairs of autosomes and one pair of sex chromosomes. What is the ploidy of this cell?

Accepted Answer

Diploid ($$2n)$$

Question 6

Which of the following statements correctly distinguishes homologous chromosomes from sister chromatids?

Accepted Answer

Homologous chromosomes are similar but may carry different alleles; sister chromatids are identical copies formed after DNA replication.

Question 7

What is the evolutionary advantage of sexual reproduction according to the purifying selection hypothesis?

Accepted Answer

Sexual reproduction allows offspring to avoid inheriting deleterious alleles present in the parent, increasing survival.

Question 8

During meiosis I, what separates during anaphase I?

Accepted Answer

Homologous chromosomes

Question 9

Which of the following events does NOT occur between meiosis I and meiosis II?

Accepted Answer

Chromosome replication

Question 10

A woman’s risk of producing an egg with an abnormal number of chromosomes increases with age. What biological process explains this phenomenon?

Accepted Answer

Primary oocytes arrest in prophase I for many years, increasing the chance of nondisjunction during meiosis.

Question 11

Which formula correctly represents the change in chromosome number during meiosis and fertilization?

Accepted Answer

$$2n \rightarrow n$$ during meiosis; $$n + n \rightarrow 2n$$ during fertilization

Question 12

Which of the following is a direct result of crossing over during meiosis?

Accepted Answer

Chromosomes with new combinations of maternal and paternal alleles

Question 13

In a population of roundworms (C. elegans), which reproductive strategy increases survival in a rapidly changing environment?

Accepted Answer

High rate of outcrossing (sexual reproduction)

Question 14

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

Accepted Answer

Replication of DNA during interphase

Question 15

What is the outcome of meiosis II in terms of chromosome number and genetic diversity?

Accepted Answer

Four haploid daughter cells, each genetically distinct due to crossing over and independent assortment

Question 16

Which of the following best describes the difference in chromosome behavior between mitosis and meiosis?

Accepted Answer

Homologous chromosomes pair and separate in meiosis, but not in mitosis.

Question 17

A cell with replicated chromosomes undergoes meiosis. What is the ploidy and chromosome structure of the resulting gametes?

Accepted Answer

Haploid ($$n) $$with unreplicated chromosomes

Question 18

Which event during meiosis ensures that each gamete is genetically unique?

Accepted Answer

Random alignment of homologous chromosomes at the metaphase plate

Question 19

What is the consequence of nondisjunction during meiosis?

Accepted Answer

Gametes with abnormal numbers of chromosomes, potentially leading to disorders such as Down syndrome

Question 20

Which hypothesis explains the evolutionary benefit of sexual reproduction in changing environments?

Accepted Answer

Changing-environment hypothesis

Meiosis: Mechanisms, Genetic Variation, and Evolutionary Significance

Study Guide - Practice Questions