Question 1

Which of the following best explains why meiosis is essential for sexually reproducing organisms?

Accepted Answer

It 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 variability among gametes.

Question 3

A human cell with 47 chromosomes, including three copies of chromosome 21, is best described as:

Accepted Answer

A case of Down syndrome (trisomy 21)

Question 4

Which of the following equations correctly represents the number of possible chromosomally different zygotes produced by humans, assuming no crossing-over?

Accepted Answer

$$(2^{23})^2$

Question 5

What is the primary difference between the alignment of chromosomes during metaphase I of meiosis and metaphase of mitosis?

Accepted Answer

In metaphase I of meiosis, tetrads align at the spindle equator; in mitosis, individual chromosomes (dyads) align separately.

Question 6

A woman over the age of 40 has an increased risk of having a child with which chromosomal abnormality, and why?

Accepted Answer

Down syndrome, due to increased nondisjunction leading to trisomy 21

Question 7

Which of the following statements about homologous chromosomes is correct?

Accepted Answer

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

Question 8

If nondisjunction occurs during meiosis II, what is the expected outcome in the resulting gametes?

Accepted Answer

Half the gametes will be normal, and half will have either an extra or missing chromosome.

Question 9

Which syndrome is characterized by a male with an extra X chromosome (47, XXY), and what is a typical feature?

Accepted Answer

Klinefelter syndrome; extra X inactivated as Barr body

Question 10

Which process is responsible for producing genetically unique gametes in humans?

Accepted Answer

Meiosis, due to crossing-over and independent assortment

Question 11

A male with the karyotype XYY is most likely to have which syndrome, and what is a common characteristic?

Accepted Answer

Jacobs syndrome; taller than average

Question 12

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

Accepted Answer

Sister chromatids are separated, resulting in four haploid cells.

Question 13

Which event ensures that chromosome number remains constant from generation to generation in sexually reproducing organisms?

Accepted Answer

Fertilization restores the diploid number after meiosis reduces it to haploid.

Question 14

Which of the following is true regarding the timing and location of meiosis in humans?

Accepted Answer

Meiosis occurs only in specialized tissues at certain times of the life cycle.

Question 15

A cell with only one copy of a particular chromosome is said to exhibit which condition?

Accepted Answer

Monosomy

Question 16

Which of the following best explains why newborns with abnormal sex chromosome numbers are more likely to survive than those with abnormal autosome numbers?

Accepted Answer

Extra X chromosomes can be inactivated as Barr bodies, reducing their impact.

Question 17

Which phase of meiosis is most directly responsible for the separation of homologous chromosomes?

Accepted Answer

Anaphase I

Question 18

Which of the following is a direct result of synapsis during prophase I?

Accepted Answer

Formation of tetrads, allowing for crossing-over between nonsister chromatids

Question 19

Which of the following best describes the genetic relationship between daughter cells produced by mitosis versus those produced by meiosis?

Accepted Answer

Mitosis produces genetically identical cells; meiosis produces genetically diverse cells.

Question 20

Which syndrome results from the absence of a second sex chromosome (45, XO), and what is a typical feature?

Accepted Answer

Turner syndrome; female phenotype

Meiosis and the Genetic Basis of Sexual Reproduction

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