Question 1

Which of the following best explains why offspring produced by sexual reproduction are genetically unique compared to their parents?

Accepted Answer

Because meiosis introduces genetic variation through crossing-over, independent assortment, and random fertilization.

Question 2

In humans, what is the value of $$n in $$the haploid number of chromosomes?

Accepted Answer

$$n = 23$$

Question 3

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

Accepted Answer

Prophase I; it increases genetic variation by exchanging genetic material between non-sister chromatids.

Question 4

If a diploid cell with 12 chromosomes undergoes meiosis, how many chromosomes will each gamete contain?

Accepted Answer

6

Question 5

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

Accepted Answer

Independent assortment during metaphase I

Question 6

What would be the result if meiosis did NOT reduce the chromosome number by half before fertilization?

Accepted Answer

The offspring would have double the chromosome number of the parents.

Question 7

Which of the following is a direct result of nondisjunction during meiosis?

Accepted Answer

Production of gametes with abnormal chromosome numbers, such as trisomy or monosomy

Question 8

A human cell with 47 chromosomes is most likely the result of which event?

Accepted Answer

Aneuploidy due to nondisjunction

Question 9

Which of the following best describes homologous chromosomes?

Accepted Answer

They are chromosomes that carry the same genes but may have different alleles, one inherited from each parent.

Question 10

In oogenesis, why is the division of cytoplasm unequal, resulting in polar bodies?

Accepted Answer

To provide one ovum with most of the cytoplasm and nutrients necessary for early development.

Question 11

Which of the following events does NOT contribute to genetic variation in sexually reproducing organisms?

Accepted Answer

Replication of DNA during S phase

Question 12

A karyotype of a human cell shows 47 chromosomes, including three copies of chromosome 21. What condition does this represent?

Accepted Answer

Down syndrome (Trisomy 21)

Question 13

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

Accepted Answer

$$n + n = 2n$$

Question 14

Which stage of meiosis is most directly responsible for reducing the chromosome number from diploid to haploid?

Accepted Answer

Meiosis I

Question 15

If a species has a diploid number of 8 chromosomes, how many possible combinations of chromosomes can be produced in its gametes due to independent assortment alone?

Accepted Answer

$$2^4 = 16$

Question 16

Which of the following is true about polyploidy?

Accepted Answer

It results in individuals with three or more sets of chromosomes and is common in plants.

Question 17

Which of the following best describes the difference between primary and secondary nondisjunction?

Accepted Answer

Primary nondisjunction is the failure of homologous chromosomes to separate during meiosis I; secondary is the failure of sister chromatids to separate during meiosis II.

Question 18

Which of the following is a key difference between meiosis and mitosis?

Accepted Answer

Meiosis involves two rounds of cell division and results in haploid cells, while mitosis involves one round and results in diploid cells.

Question 19

A woman aged 45 has a higher risk of having a child with Down syndrome compared to a woman aged 25. What is the most likely biological explanation for this?

Accepted Answer

The likelihood of nondisjunction increases with maternal age.

Meiosis and Sexual Reproduction: Mechanisms, Consequences, and Chromosomal Variation

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