Question 1

Which of the following best explains why meiosis is necessary for sexual reproduction in humans?

Accepted Answer

It reduces the chromosome number by half in gametes, preventing chromosome doubling after fertilization.

Question 2

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

Accepted Answer

Crossing over occurs during prophase I and increases genetic variation among gametes.

Question 3

A human cell with 46 chromosomes undergoes meiosis. How many chromosomes will each resulting gamete contain?

Accepted Answer

$$23$$

Question 4

If meiosis did not reduce the chromosome number in gametes, what would be the chromosome number in the zygote after fertilization in humans?

Accepted Answer

$$92$$

Question 5

Which of the following events contributes most directly to the genetic uniqueness of siblings (excluding identical twins)?

Accepted Answer

Crossing over and independent assortment during meiosis

Question 6

A child is born with three copies of chromosome 21. Which meiotic error most likely caused this condition?

Accepted Answer

Nondisjunction during anaphase I or II

Question 7

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

Accepted Answer

Homologous chromosomes are a pair, one from each parent, with the same genes but possibly different alleles; sister chromatids are identical copies formed by DNA replication.

Question 8

Which process is responsible for the random distribution of maternal and paternal chromosomes into gametes?

Accepted Answer

Independent assortment

Question 9

In a species where $$2n = 8$$, how many genetically distinct gametes can be produced by independent assortment alone (ignoring crossing over)?

Accepted Answer

$$2^4 = 16$

Question 10

Which of the following statements about meiosis and mitosis is correct?

Accepted Answer

Meiosis produces four genetically unique haploid cells, while mitosis produces two genetically identical diploid cells.

Question 11

A woman with genotype $$Pp$$ for flower color (where $$P is $$dominant for purple and $$p is $$recessive for white) is considered:

Accepted Answer

Heterozygous

Question 12

Which of the following best explains why genetic variation is advantageous for a population?

Accepted Answer

It increases the likelihood that some individuals possess traits that allow survival in changing environments.

Question 13

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

Accepted Answer

Anaphase I

Question 14

Which of the following is a direct consequence if a human gamete receives no sex chromosome during meiosis?

Accepted Answer

The resulting zygote will be inviable if fertilized by a Y-bearing sperm.

Question 15

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

Accepted Answer

Sister chromatids are separated, resulting in four haploid cells.

Question 16

A karyotype is most useful for which of the following purposes?

Accepted Answer

Visualizing the number and structure of chromosomes in a cell

Question 17

Which of the following is true regarding the difference between a locus and an allele?

Accepted Answer

A locus is the physical location of a gene on a chromosome, while an allele is a specific version of that gene.

Question 18

Which of the following best explains why asexual reproduction results in less genetic variation than sexual reproduction?

Accepted Answer

Asexual reproduction produces offspring that are genetically identical to the parent, except for rare mutations.

Question 19

Which of the following scenarios is an example of polygenic inheritance?

Accepted Answer

Multiple genes contribute to the variation in human skin color.

Question 20

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

Accepted Answer

Chromosomes condense in both, but only in prophase I of meiosis do homologous chromosomes pair and crossing over occurs.

Meiosis and Genetic Variation: Molecular Biology of the Gene (Ch. 10)

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