Question 1

Which of the following best explains why offspring produced by sexual reproduction are not identical to their parents?

Accepted Answer

Meiosis and fertilization shuffle alleles and produce new combinations of genes.

Question 2

In humans, how many possible combinations of chromosomes can result from independent assortment during gamete formation? Use $$n = 23$$ for the haploid number.

Accepted Answer

$$2^{23}$$, which is over 8 million possible combinations.

Question 3

Which event is unique to meiosis and does NOT occur in mitosis?

Accepted Answer

Synapsis and crossing over between homologous chromosomes.

Question 4

A diploid cell in a human has $$2n = 46$$ chromosomes. After meiosis II, how many chromosomes will each daughter cell contain?

Accepted Answer

23 chromosomes

Question 5

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 6

Which of the following statements about homologous chromosomes is TRUE?

Accepted Answer

They carry genes controlling the same inherited characters but may have different alleles.

Question 7

If a mutation occurs in a gene located on a chromosome, what is the most direct way this mutation can be passed to offspring?

Accepted Answer

If the mutation is present in a gamete that participates in fertilization.

Question 8

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

Accepted Answer

Fertilization

Question 9

A plant exhibits alternation of generations. Which statement best describes this life cycle?

Accepted Answer

It alternates between multicellular diploid and multicellular haploid stages.

Question 10

Which mechanism does NOT contribute to genetic variation in sexually reproducing organisms?

Accepted Answer

Replication of DNA during mitosis

Question 11

A geneticist observes that two siblings have different combinations of traits. Which process is MOST responsible for this difference?

Accepted Answer

Independent assortment of chromosomes during meiosis

Question 12

Which of the following best describes the difference between meiosis I and meiosis II?

Accepted Answer

Meiosis I separates homologous chromosomes; meiosis II separates sister chromatids.

Question 13

If a human zygote is formed by the fusion of two gametes, each with $$8.4 	imes 10^6$ possible chromosome combinations, what is the approximate number of possible diploid combinations in the zygote?

Accepted Answer

$$(8.4 	imes 10^6$)^2$$ \approx 70 	imes $$10^{12}$

Question 14

Which of the following is TRUE about the products of meiosis in animals?

Accepted Answer

Each product is genetically unique due to crossing over and independent assortment.

Question 15

During which stage of meiosis do homologous chromosomes align at the metaphase plate?

Accepted Answer

Metaphase I

Question 16

Which statement best describes the role of cohesins during meiosis?

Accepted Answer

Cohesins hold sister chromatids together until they are separated during anaphase II.

Question 17

A scientist observes a cell with duplicated chromosomes, each consisting of two sister chromatids. Which phase of meiosis could this cell be in?

Accepted Answer

Prophase I

Question 18

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

Accepted Answer

Formation of recombinant chromosomes containing DNA from both parents.

Question 19

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

Accepted Answer

Meiosis requires homologous pairs of chromosomes to align and separate.

Question 20

Which of the following mechanisms is responsible for the halving and subsequent doubling of chromosome number in sexual life cycles?

Accepted Answer

Meiosis halves the chromosome number; fertilization doubles it.

Ch. 13 Meiosis and Sexual Life Cycles – Study Notes

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