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. How many chromosomes and how much DNA (relative to a gamete) are present in each daughter cell at the end of meiosis II?

Accepted Answer

2 chromosomes, 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

If an organism has a diploid number of 6 (2n = 6), how many genetically unique gametes can it produce due to independent assortment alone (ignoring crossing over)? Use the formula $$2^n.$$

Accepted Answer

$$2^3 = 8$

Question 5

Which event distinguishes meiosis I from mitosis?

Accepted Answer

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

Question 6

A human cell in metaphase II of meiosis contains 23 chromosomes. How many chromatids are present in this cell?

Accepted Answer

46 chromatids

Question 7

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

Accepted Answer

Binary fission

Question 8

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 9

Which of the following best describes the Law of Segregation?

Accepted Answer

Homologous chromosomes separate during anaphase I of meiosis, so each gamete receives only one allele of each gene.

Question 10

A cell with genotype AaBb undergoes meiosis. If no crossing over occurs, what is the expected ratio of gamete genotypes due to independent assortment?

Accepted Answer

1 AB : 1 Ab : 1 aB : 1 ab

Question 11

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

Accepted Answer

Fertilization

Question 12

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

Accepted Answer

Mitosis produces two genetically identical diploid cells, while meiosis produces four genetically unique haploid cells.

Question 13

During which stage of meiosis do homologous chromosomes align at the metaphase plate, allowing for independent assortment?

Accepted Answer

Metaphase I

Question 14

Which of the following best explains why siblings from the same parents can look very different from each other?

Accepted Answer

Genetic variation is introduced by crossing over, independent assortment, and random fertilization.

Question 15

Which of the following events occurs only during meiosis and not during mitosis?

Accepted Answer

Pairing of homologous chromosomes and crossing over

Question 16

A mutation occurs in a gene during DNA replication in a germ cell. Which of the following is true regarding the inheritance of this mutation?

Accepted Answer

The mutation can be passed to offspring if it is present in a gamete that participates in fertilization.

Question 17

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

Accepted Answer

Homologous chromosomes are similar but not identical, each inherited from a different parent; sister chromatids are identical copies formed by DNA replication.

Question 18

Which of the following is a direct result of the Law of Independent Assortment?

Accepted Answer

Genes located on different chromosomes are inherited independently of each other.

Question 19

In a human, how many possible chromosome combinations can result from independent assortment alone during gamete formation? Use the formula $$2^{23}.$$

Accepted Answer

$$2^{23} = 8$$,388,608$$

Question 20

Which of the following best explains why meiosis is necessary for sexual reproduction in humans?

Accepted Answer

Meiosis reduces the chromosome number by half, ensuring that fertilization restores the diploid number.

Inheritance and Sources of Genetic Variation: Meiosis, Mitosis, and Mendelian Laws

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