Question 1

Which phase of the cell cycle is characterized by high levels of gene expression and preparation for DNA synthesis?

Accepted Answer

G\_1 (Gap 1) phase

Question 2

During mitosis, what is the primary function of the centromere?

Accepted Answer

To bind spindle fiber microtubules and join sister chromatids

Question 3

A cell with a diploid number of chromosomes ($2n$) undergoes mitosis. What is the chromosome number in each daughter cell after division?

Accepted Answer

$2n$

Question 4

Which event distinguishes meiosis I from mitosis?

Accepted Answer

Pairing and crossing over of homologous chromosomes

Question 5

In animal cells, what structure is responsible for the formation of the cleavage furrow during cytokinesis?

Accepted Answer

Contractile ring of actin

Question 6

Which of the following best explains why gametes produced by meiosis are not genetically identical?

Accepted Answer

Crossing over and independent assortment during meiosis I

Question 7

A male Drosophila fly has the genotype XYY. According to the X/autosome ratio, what is its phenotypic sex?

Accepted Answer

Male, because the X/A ratio is 0.5

Question 8

Which protein is responsible for cleaving cohesin and allowing sister chromatids to separate during anaphase?

Accepted Answer

Separase

Question 9

What is the mechanical basis for Mendel's law of segregation as explained by meiosis?

Accepted Answer

Separation of homologous chromosomes during anaphase I

Question 10

Which of the following is a hallmark of X-linked recessive inheritance in humans?

Accepted Answer

Trait is expressed much more often in males than females

Question 11

A female mammal is heterozygous for an X-linked gene. What is the expected pattern of gene expression in her somatic cells?

Accepted Answer

Some cells express the maternal X and others the paternal X, resulting in a mosaic

Question 12

Which gene is essential for random X-chromosome inactivation in placental mammals?

Accepted Answer

XIST

Question 13

A cell is observed to have 46 chromosomes and 92 chromatids during a particular phase of the cell cycle. Which phase is this?

Accepted Answer

S phase

Question 14

Which of the following mechanisms equalizes gene expression between males and females in species with sex chromosomes?

Accepted Answer

Dosage compensation

Question 15

In mammals, what is the role of the SRY gene?

Accepted Answer

Initiates testicular development by producing a transcription factor

Question 16

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

Accepted Answer

Mitosis produces diploid cells, while meiosis II produces haploid cells

Question 17

A rare event during meiosis results in a female Drosophila with two X chromosomes and one Y chromosome. What is the most likely explanation for this genotype?

Accepted Answer

Nondisjunction of sex chromosomes during meiosis

Question 18

Which stage of prophase I in meiosis is characterized by the formation of the synaptonemal complex?

Accepted Answer

Zygotene

Question 19

Which of the following is true about the product of meiosis in a diploid organism?

Accepted Answer

Four genetically distinct haploid cells

Question 20

Which process during meiosis is responsible for generating Mendelian ratios of allele segregation?

Accepted Answer

Separation of homologous chromosomes during anaphase I

3. Cell Division and Chromosome Heredity

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