Question 1

Which of the following best describes the difference between a diploid (2n) and a haploid (n) cell in humans?

Accepted Answer

A diploid cell contains two sets of chromosomes, one from each parent, while a haploid cell contains only one set.

Question 2

During which phase of meiosis does crossing over occur, and what is its significance?

Accepted Answer

Crossing over occurs during prophase I and increases genetic variation by exchanging DNA between homologous chromosomes.

Question 3

A human zygote is formed by the fusion of two gametes. What is the chromosome number of the zygote, and which process restores this number after gamete formation?

Accepted Answer

The zygote is diploid (2n = 46), and fertilization restores the diploid number after meiosis reduces it in gametes.

Question 4

Which of the following is NOT a mechanism that contributes to genetic variation in sexually reproducing organisms?

Accepted Answer

Replication of DNA during interphase

Question 5

If a species has a haploid number $$n = 4$$, how many possible combinations of chromosomes can result from independent assortment during gamete formation?

Accepted Answer

$$2^4 = 16$

Question 6

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

Accepted Answer

Synapsis and crossing over between homologous chromosomes

Question 7

A male human karyotype shows 46 chromosomes, including one X and one Y chromosome. Which statement is correct regarding the sex chromosomes?

Accepted Answer

The X and Y chromosomes are not homologous but pair during meiosis I.

Question 8

During which stage of meiosis do homologous chromosomes separate, and what is the result for the daughter cells?

Accepted Answer

Anaphase I; each daughter cell receives a haploid set of chromosomes, each still consisting of two sister chromatids.

Question 9

Which of the following best explains why siblings from the same parents can look very different from each other?

Accepted Answer

Independent assortment, crossing over, and random fertilization create unique combinations of alleles in each offspring.

Question 10

Which process is responsible for producing gametes in humans, and what is the chromosome number in these gametes?

Accepted Answer

Meiosis; gametes are haploid with $$n = 23$$ chromosomes.

Question 11

A mutation occurs in a gene located on chromosome 7. If this mutation is present in a gamete that participates in fertilization, what is the likely outcome?

Accepted Answer

The mutation will be present in all somatic cells of the resulting offspring.

Question 12

Which of the following statements about homologous chromosomes is correct?

Accepted Answer

They carry the same genes at the same loci, but may have different alleles.

Question 13

In a plant species, the diploid number is 8. After meiosis, how many chromosomes will each gamete contain?

Accepted Answer

4

Question 14

Which of the following best describes the role of meiosis in the human life cycle?

Accepted Answer

Meiosis reduces the chromosome number by half, producing haploid gametes that restore diploidy upon fertilization.

Question 15

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

Accepted Answer

Recombinant chromosomes with new combinations of maternal and paternal alleles.

Question 16

A couple has a child with a genetic disorder caused by a new mutation. Which statement best explains the origin of this mutation?

Accepted Answer

The mutation likely arose in a gamete of one parent and was passed to the zygote during fertilization.

Question 17

Which of the following equations correctly represents the number of possible chromosome combinations due to independent assortment in a species with a haploid number $$n$$?

Accepted Answer

$$2^n$$

Question 18

Why is random fertilization a significant source of genetic variation?

Accepted Answer

Because any sperm can fuse with any egg, creating a zygote with a unique combination of alleles.

Question 19

Which of the following best describes the outcome of meiosis II?

Accepted Answer

Separation of sister chromatids, resulting in four haploid cells with unduplicated chromosomes.

Meiosis, Sexual Life Cycles, and Genetic Variation

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