Question 1

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

Accepted Answer

Because independent assortment, crossing over, and random fertilization create new combinations of alleles.

Question 2

A human cell containing 22 autosomes and an X chromosome could be:

Accepted Answer

A sperm cell.

Question 3

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

Accepted Answer

Synapsis and crossing over between homologous chromosomes.

Question 4

If an organism has a diploid number of $$2n = 12$$, how many possible combinations of chromosomes can be produced in its gametes by independent assortment alone?

Accepted Answer

$$2^{6} = 64$

Question 5

During which phase of meiosis do homologous chromosomes separate and move toward opposite poles?

Accepted Answer

Anaphase I

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 statements about meiosis is TRUE?

Accepted Answer

Meiosis reduces the chromosome number by half, resulting in haploid cells.

Question 8

A mutation occurs in a gene located on a chromosome. What is the most likely way this mutation can be passed to the next generation?

Accepted Answer

If the mutation occurs in a gamete produced by meiosis.

Question 9

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

Accepted Answer

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

Question 10

Which process is responsible for the formation of recombinant chromosomes during meiosis?

Accepted Answer

Crossing over

Question 11

Why is it that only diploid cells can undergo meiosis?

Accepted Answer

Because only diploid cells have homologous pairs of chromosomes that can be separated.

Question 12

If a human egg (n = 23) is fertilized by a sperm (n = 23), what is the chromosome number of the resulting zygote?

Accepted Answer

$$2n = 46$$

Question 13

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

Accepted Answer

Replication of DNA during interphase

Question 14

A scientist observes a cell with two sets of chromosomes, each consisting of two sister chromatids, aligned at the metaphase plate. Which stage is this cell most likely in?

Accepted Answer

Metaphase II of meiosis

Question 15

Which of the following best explains why asexual reproduction results in offspring that are genetically identical to the parent?

Accepted Answer

Because all genes are passed to offspring without the fusion of gametes, and there is no mixing of alleles.

Question 16

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

Accepted Answer

23

Question 17

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

Accepted Answer

The formation of recombinant chromosomes.

Question 18

A geneticist is studying a population of animals that reproduce sexually. Which of the following would most likely increase genetic variation in the next generation?

Accepted Answer

An increase in the mutation rate in gametes.

Question 19

Which of the following statements about the evolutionary significance of genetic variation is correct?

Accepted Answer

Natural selection acts on genetic variation, favoring traits that are advantageous in a given environment.

Question 20

A researcher observes that a certain fungus produces gametes by mitosis, and the only diploid stage is the zygote. Which type of sexual life cycle does this fungus exhibit?

Accepted Answer

Fungal/protist life cycle

Meiosis, Sexual Life Cycles, and Genetic Variation

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