Question 1

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

Accepted Answer

Crossing over occurs during prophase I and results in the exchange of genetic material between homologous chromosomes, increasing genetic diversity.

Question 2

If a human cell has a diploid number of 46 chromosomes ($$2n = 46$$), how many chromosomes will each gamete have after meiosis?

Accepted Answer

$$23$$

Question 3

Which of the following mechanisms does NOT contribute to genetic variation during sexual reproduction?

Accepted Answer

Replication of DNA during interphase

Question 4

A woman over age 35 is at increased risk for nondisjunction during meiosis. What is the most likely consequence if nondisjunction occurs in meiosis I?

Accepted Answer

Half of the gametes will have an extra chromosome, and half will lack one.

Question 5

Which event distinguishes anaphase I from anaphase II in meiosis?

Accepted Answer

Homologous chromosomes separate in anaphase I, while sister chromatids separate in anaphase II.

Question 6

A zygote is formed by the fusion of two gametes. If one gamete has 24 chromosomes due to nondisjunction and the other is normal, what will be the chromosome number in the resulting zygote?

Accepted Answer

$$47$$

Question 7

Which process is responsible for reducing the chromosome number by half during gamete formation?

Accepted Answer

Meiosis

Question 8

Why are the four daughter cells produced by meiosis genetically non-identical?

Accepted Answer

Because of crossing over and independent assortment during meiosis.

Question 9

Which of the following best describes independent assortment?

Accepted Answer

The random distribution of homologous chromosomes to daughter cells during meiosis I.

Question 10

If a population experienced a mutation that eliminated crossing over, which of the following outcomes would you predict?

Accepted Answer

Genetic diversity among gametes would decrease.

Question 11

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

Accepted Answer

Mitosis results in diploid cells, while meiosis results in haploid cells.

Question 12

Which stage of meiosis is responsible for the separation of homologous chromosomes?

Accepted Answer

Anaphase I

Question 13

Random fertilization increases genetic diversity because:

Accepted Answer

Any sperm can fertilize any egg, combining unique genetic material from both parents.

Question 14

A student claims that mitosis and meiosis are identical except mitosis produces half the chromosomes. Evaluate the statement.

Accepted Answer

Incorrect, because mitosis produces identical cells and does not reduce chromosome number.

Question 15

If nondisjunction occurs during meiosis II, what is the result?

Accepted Answer

Half the gametes will be normal, and half will have an abnormal chromosome number.

Question 16

Which of the following best describes a haploid cell?

Accepted Answer

A cell with one set of chromosomes ($$n)$$

Question 17

Why does meiosis have two divisions?

Accepted Answer

To ensure that chromosome number is reduced by half and to separate sister chromatids.

Question 18

During which stage of meiosis does independent assortment occur?

Accepted Answer

Anaphase I

Question 19

What is the final product of meiosis in terms of chromosome number and genetic makeup?

Accepted Answer

Four haploid cells, each genetically unique

Question 20

If each human gamete can produce $$8 	imes 10^6$ million combinations of chromosomes (due to independent assortment), how does random fertilization affect possible zygote combinations?

Accepted Answer

It multiplies combinations between gametes from both parents, increasing genetic diversity.

Meiosis, Sexual Life Cycle, and Genetic Variation: Study Guide

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