Question 1

In the life cycle of animals, which of the following best explains why gametes are the only haploid cells?

Accepted Answer

Because meiosis directly produces gametes, and all other cells arise from mitotic divisions of the diploid zygote.

Question 2

Which of the following distinguishes a spore from a gamete in plant life cycles?

Accepted Answer

A spore can develop into a multicellular organism without fertilization, while a gamete must fuse with another gamete to develop further.

Question 3

In the context of meiosis, why are two chromosome-separation events required even though DNA replicates only once?

Accepted Answer

To separate homologous chromosomes in meiosis I and sister chromatids in meiosis II, ensuring the reduction of chromosome number from diploid to haploid.

Question 4

During meiosis I, what is paired and what separates?

Accepted Answer

Homologous chromosomes are paired and separate, while sister chromatids remain joined at the centromere.

Question 5

If an organism has three pairs of homologous chromosomes ($$n = 3$$), how many different combinations of chromosomes are possible in its gametes due to independent assortment?

Accepted Answer

$$2^3 = 8$

Question 6

Which event during meiosis is primarily responsible for generating recombinant chromosomes that neither parent possessed?

Accepted Answer

Crossing over between nonsister chromatids during prophase I.

Question 7

Why does the orientation of one homologous chromosome pair at metaphase I not determine the orientation of another pair?

Accepted Answer

Each pair aligns independently due to random orientation at the metaphase plate, leading to independent assortment.

Question 8

How did seed plants solve the problem of gametes needing water to find each other, allowing them to colonize land?

Accepted Answer

By evolving pollen grains that transport sperm cells through the air, eliminating the need for water for fertilization.

Question 9

Which of the following best explains the evolutionary advantage of having both haploid and diploid phases in a life cycle?

Accepted Answer

It increases genetic variation and allows for the masking of deleterious mutations in the diploid phase.

Question 10

If a single chiasma occurs between two homologous chromosomes during meiosis, what is the result?

Accepted Answer

Two recombinant chromatids and two parental (unchanged) chromatids.

Question 11

Which of the following is NOT a consequence of meiosis?

Accepted Answer

Mutation of individual genes, such as deletions.

Question 12

In ferns, how does diploid tissue protect the haploid generation from drying out compared to angiosperms?

Accepted Answer

In ferns, the haploid gametophyte is exposed and vulnerable, while in angiosperms, the haploid generation is protected within diploid tissues (e.g., ovule and pollen grain).

Question 13

Which of the following best describes the chromosome content of a gamete produced by meiosis?

Accepted Answer

It contains one chromosome from each homologous pair, representing a haploid set.

Question 14

If one pair of homologous chromosomes fails to assort independently (is linked to another pair), what is the effect on the number of possible gamete combinations?

Accepted Answer

The number of possible combinations decreases because the linked chromosomes are inherited together.

Question 15

Which process is most similar to the separation of sister chromatids in meiosis II?

Accepted Answer

The separation of sister chromatids during mitosis.

Question 16

A diploid cell with $$2n = 8$$ undergoes meiosis. How many chromosomes will each resulting gamete contain?

Accepted Answer

$$n = 4$$

Question 17

Which of the following is a direct result of independent assortment during meiosis?

Accepted Answer

Gametes with different combinations of maternal and paternal chromosomes.

Question 18

Why is the number of possible chromosome combinations in human gametes $$2^{23}$$?

Accepted Answer

Because each of the 23 homologous chromosome pairs can orient independently during metaphase I.

Question 19

Which of the following best describes the outcome if meiosis occurred without crossing over?

Accepted Answer

Gametes would have new combinations of chromosomes due to independent assortment, but no new combinations within chromosomes.

Question 20

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

Accepted Answer

Meiosis II starts with haploid cells, while mitosis usually starts with diploid cells.

Guided Study for BIO 1305 Chapter 13: Sexual Life Cycles and Genetic Variation

Guida di studio - Domande di pratica

Study guide - Flashcard