Question 1

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

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 is:

Accepted Answer

An egg cell.

Question 3

During which phase of meiosis does crossing over occur, and what is the significance of this event?

Accepted Answer

Crossing over occurs during prophase I and increases genetic variation by exchanging DNA between nonsister chromatids.

Question 4

If an organism has a diploid number of 8 ($$2n = 8$$), how many possible combinations of chromosomes can result from independent assortment during meiosis?

Accepted Answer

$$2^4 = 16$

Question 5

Which of the following statements about homologous chromosomes is correct?

Accepted Answer

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

Question 6

In the life cycle of most fungi and some protists, which of the following is true?

Accepted Answer

The only diploid stage is the single-celled zygote.

Question 7

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

Accepted Answer

Pairing of homologous chromosomes and crossing over.

Question 8

A diploid cell with $$2n = 6$$ undergoes meiosis. How many chromosomes and DNA molecules are present in each daughter cell at the end of meiosis II?

Accepted Answer

3 chromosomes and 3 DNA molecules.

Question 9

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

Accepted Answer

Meiosis

Question 10

In humans, how many genetically distinct gametes can be produced by independent assortment alone?

Accepted Answer

$$2^{23}$$

Question 11

Which of the following best describes the alternation of generations in plants?

Accepted Answer

Plants alternate between a multicellular diploid sporophyte and a multicellular haploid gametophyte.

Question 12

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

Accepted Answer

Replication of DNA during S phase.

Question 13

A mutation occurs in a gene located on a chromosome. What is the most direct result of this mutation?

Accepted Answer

A new allele is created at the gene's locus.

Question 14

Which of the following is true regarding the separation of chromatids and homologous chromosomes during meiosis?

Accepted Answer

Homologous chromosomes separate during anaphase I, and sister chromatids separate during anaphase II.

Question 15

Which of the following best explains why asexual reproduction is advantageous in a stable environment?

Accepted Answer

It perpetuates successful combinations of alleles without introducing variation.

Question 16

Which of the following statements about gametes in animals is correct?

Accepted Answer

Gametes are the only haploid cells in animals and are produced by meiosis.

Question 17

A cell with a diploid number of 10 ($$2n = 10) $$undergoes meiosis. After meiosis I, how many chromosomes are present in each daughter cell, and are they duplicated or unduplicated?

Accepted Answer

5 chromosomes, each consisting of two sister chromatids (duplicated).

Question 18

Which of the following is a direct result of random fertilization in humans?

Accepted Answer

Each zygote has a unique combination of alleles from both parents, with about 70 trillion possible combinations.

Question 19

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

Accepted Answer

Both processes separate sister chromatids, but mitosis starts with a diploid cell and meiosis II starts with a haploid cell.

Meiosis and Sexual Life Cycles (Chapter 13) – Study Notes

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