Question 1

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

Accepted Answer

Meiosis reduces the chromosome number by half, preventing chromosome doubling in each generation.

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 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 nondisjunction occurs during meiosis I in a human female, which of the following could result?

Accepted Answer

Some gametes may have two copies of a chromosome, while others have none.

Question 5

Which of the following statements about homologous chromosomes is correct?

Accepted Answer

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

Question 6

A child is born with trisomy 21 (Down syndrome). Which meiotic error most likely caused this condition?

Accepted Answer

Nondisjunction of chromosome 21 during meiosis, resulting in a gamete with an extra chromosome.

Question 7

Which process is responsible for the vast genetic diversity observed in sexually reproducing populations?

Accepted Answer

Crossing over and independent assortment during meiosis.

Question 8

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 9

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

Accepted Answer

Meiosis I reduces the chromosome number by half, while meiosis II separates sister chromatids.

Question 10

A heterozygous individual for flower color has the genotype $$Pp. $$What does this mean in terms of alleles and chromosomes?

Accepted Answer

One homologous chromosome carries the $$P$$ allele and the other carries the $$p$$ allele.

Question 11

Which of the following events occurs during metaphase I of meiosis but not during metaphase of mitosis?

Accepted Answer

Homologous chromosomes align as pairs at the metaphase plate.

Question 12

Why is genetic variation from meiosis advantageous for populations living in changing environments?

Accepted Answer

It increases the likelihood that some individuals will possess traits suited for survival.

Question 13

Which of the following is true regarding the chromosome number in gametes and zygotes in humans?

Accepted Answer

Gametes are haploid ($$n) $$and zygotes are diploid ($$2n).$$

Question 14

Which of the following best describes a locus?

Accepted Answer

The physical location of a gene on a chromosome.

Question 15

Which of the following is a key difference between asexual and sexual reproduction?

Accepted Answer

Sexual reproduction produces offspring with greater genetic diversity due to meiosis.

Question 16

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

Accepted Answer

Anaphase I

Question 17

If a mutation occurs in a gene located on a homologous chromosome, which of the following is most likely to happen in the next generation?

Accepted Answer

The mutation may be passed on if the gamete carrying it is involved in fertilization.

Question 18

Which of the following best explains why individuals produced by sexual reproduction (except identical twins) are genetically unique?

Accepted Answer

Crossing over and independent assortment during meiosis create new combinations of alleles.

Question 19

Which of the following is a correct comparison between mitosis and meiosis?

Accepted Answer

Mitosis maintains chromosome number, while meiosis halves it.

Question 20

A woman with genotype $$X ($$only one X chromosome) is born. Which chromosomal event most likely led to this condition?

Accepted Answer

Nondisjunction during meiosis resulting in a gamete missing an X chromosome.

Meiosis, Chromosome Behavior, and Genetic Variation: Study Notes for General Biology

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