Question 1

Which of the following statements best explains why offspring produced by sexual reproduction are genetically different from their parents?

Accepted Answer

Because sexual reproduction involves the combination of genes from two parents, independent assortment, crossing over, and random fertilization.

Question 2

A human cell containing 22 autosomes and an X chromosome is:

Accepted Answer

A gamete, which could be either an egg or a sperm

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 DNA between homologous chromosomes

Question 4

If an organism has a diploid number of 8 ($$2n = 8$$), how many possible combinations of chromosomes can be produced in its gametes due to independent assortment alone?

Accepted Answer

$$2^4 = 16$

Question 5

Which of the following events occurs in meiosis but NOT in mitosis?

Accepted Answer

Pairing of homologous chromosomes and crossing over

Question 6

A plant species has a life cycle that includes both multicellular diploid and multicellular haploid stages. This is an example of:

Accepted Answer

Alternation of generations

Question 7

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

Accepted Answer

Homologous chromosomes are inherited from each parent and may have different alleles; sister chromatids are identical copies formed after DNA replication.

Question 8

A geneticist observes a cell with 23 chromosomes, each consisting of two sister chromatids, aligned at the metaphase plate. This cell is most likely in:

Accepted Answer

Metaphase II of meiosis

Question 9

Which process is responsible for the halving of chromosome number in gametes?

Accepted Answer

Meiosis

Question 10

If a mutation occurs in a gene located on the X chromosome, which individual is more likely to express the mutant phenotype, and why?

Accepted Answer

A male, because he has only one X chromosome and no second copy to mask the mutation

Question 11

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

Accepted Answer

Replication of DNA during interphase

Question 12

A zygote is formed by the fusion of two gametes. If each gamete in humans can have $$2^{23}$$ possible chromosome combinations, how many possible chromosome combinations can a zygote have (ignoring crossing over)?

Accepted Answer

$$2^{46}$$

Question 13

Which of the following best explains why only diploid cells can undergo meiosis?

Accepted Answer

Because only diploid cells have homologous chromosome pairs that can be separated during meiosis I

Question 14

In humans, how many chromosomes are present in each cell at the end of meiosis II?

Accepted Answer

23

Question 15

Which of the following scenarios would most likely result in a genetic disorder due to nondisjunction during meiosis?

Accepted Answer

A gamete receives two copies of chromosome 21 and fuses with a normal gamete

Question 16

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

Accepted Answer

Formation of recombinant chromosomes

Question 17

A scientist is studying a fungus with a life cycle in which the only diploid stage is the zygote. What process must occur immediately after fertilization to restore the haploid state?

Accepted Answer

Meiosis

Question 18

Which of the following best describes the evolutionary significance of sexual reproduction?

Accepted Answer

It increases genetic variation, allowing populations to adapt to changing environments.

Question 19

In a certain species, the diploid number is 10 ($$2n = 10). $$After meiosis II, how many chromosomes will each gamete contain?

Accepted Answer

5

Question 20

Which of the following statements about asexual reproduction is correct?

Accepted Answer

It produces clones that are genetically identical to the parent.

Meiosis and Sexual Life Cycles: Mechanisms of Inheritance and Genetic Variation

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