Question 1

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

Accepted Answer

It reduces the chromosome number by half, so that fertilization restores the diploid state.

Question 2

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

Accepted Answer

Crossing over occurs in Prophase I and creates new allele combinations on chromosomes.

Question 3

A cell with a diploid number of $$2n = 8$$ undergoes meiosis. How many chromosomes will each resulting gamete contain?

Accepted Answer

$$4$$

Question 4

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

Accepted Answer

Homologous chromosomes have the same genes at the same loci but may have different alleles; sister chromatids are identical copies formed after DNA replication.

Question 5

If a human cell undergoes nondisjunction during Meiosis I, what is the most likely chromosomal outcome in the resulting gametes?

Accepted Answer

Half the gametes will have an extra chromosome (n+1), and half will have one less (n-1).

Question 6

Which of the following is NOT a source of genetic variation in sexually reproducing organisms?

Accepted Answer

Replication of DNA during S phase

Question 7

A karyotype of a patient shows 47 chromosomes, including three copies of chromosome 21. Which condition does this individual have?

Accepted Answer

Down Syndrome (Trisomy 21)

Question 8

Which equation correctly represents the number of possible chromosome combinations due to independent assortment in a human gamete, where $$n is $$the haploid number?

Accepted Answer

$$2^n$$

Question 9

During which phase of meiosis do homologous chromosomes separate, and what is the result for the chromosome number in the daughter cells?

Accepted Answer

Anaphase I; daughter cells become haploid

Question 10

Which of the following best distinguishes meiosis from mitosis?

Accepted Answer

Meiosis involves two rounds of cell division and produces haploid gametes; mitosis involves one division and produces diploid somatic cells.

Question 11

A woman is a carrier for a recessive allele located on an autosome. Which statement about her gametes is correct?

Accepted Answer

Half her gametes will carry the recessive allele due to independent assortment.

Question 12

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

Accepted Answer

Pairing of homologous chromosomes (synapsis) and formation of tetrads

Question 13

A male with Klinefelter Syndrome has the karyotype $$47,XXY. $$Which of the following best explains how this chromosomal abnormality can arise?

Accepted Answer

Nondisjunction of sex chromosomes during meiosis in either parent

Question 14

Which of the following statements about gametogenesis is correct?

Accepted Answer

Spermatogenesis occurs in the testes and produces sperm.

Question 15

A cell in Metaphase II of meiosis contains $$n$$ chromosomes, each consisting of two sister chromatids. What will be the chromosome number and chromatid number in each daughter cell after Telophase II?

Accepted Answer

$$n$$ chromosomes, each with one chromatid

Question 16

Which of the following best describes aneuploidy?

Accepted Answer

A cell with an abnormal number of chromosomes, such as trisomy or monosomy

Question 17

A geneticist observes a cell with duplicated chromosomes aligned in pairs at the equator. Which phase is this, and what key event is about to occur?

Accepted Answer

Metaphase I; homologous chromosomes will separate

Question 18

Which of the following scenarios would most likely result in a zygote with monosomy?

Accepted Answer

A gamete missing a chromosome fuses with a normal gamete during fertilization

Question 19

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

Accepted Answer

Crossing over and independent assortment during meiosis create unique combinations of alleles in each gamete.

Question 20

Which of the following is true regarding the chromosome content of a human somatic cell versus a human gamete?

Accepted Answer

A somatic cell is diploid ($$2n = 46) $$and a gamete is haploid ($$n = 23).$$

Meiosis: Mechanisms, Genetic Variation, and Human Implications

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