Question 1

Which of the following best describes the main difference between mitosis and meiosis in terms of chromosome number in the resulting cells?

Accepted Answer

Mitosis produces two diploid cells, while meiosis produces four haploid cells.

Question 2

During which phase of the cell cycle does DNA replication occur, and what is the result in terms of chromatid number?

Accepted Answer

DNA replication occurs during S phase, resulting in two chromatids per chromosome.

Question 3

A mutation in the gene encoding the protein separase would most likely disrupt which stage of mitosis?

Accepted Answer

Anaphase, because sister chromatids would not separate.

Question 4

Which of the following equations correctly represents the relationship between chromosome number ($$n$$), diploid number ($$2n$$), and the number of chromatids after S phase in a human somatic cell?

Accepted Answer

$$2n = 46$$, chromatids = 92$

Question 5

Which of the following best explains why gametes produced by meiosis are genetically unique?

Accepted Answer

Crossing over and independent assortment during meiosis I.

Question 6

A cell is observed to have chromosomes aligned at the metaphase plate, with spindle fibers attached to kinetochores on both sides of each centromere. Which stage is this cell in, and what is the next major event?

Accepted Answer

Metaphase; the next event is the separation of sister chromatids during anaphase.

Question 7

Which checkpoint in the cell cycle ensures that all chromosomes are properly attached to the mitotic spindle before proceeding?

Accepted Answer

Metaphase checkpoint

Question 8

In a plant cell, what structure forms during cytokinesis to separate the two daughter cells, and how does this differ from animal cells?

Accepted Answer

A cell plate forms in plant cells, while a cleavage furrow forms in animal cells.

Question 9

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

Accepted Answer

Formation of the synaptonemal complex and crossing over

Question 10

A cell with genotype AaBb undergoes meiosis. According to the law of independent assortment, what is the expected ratio of gamete genotypes produced?

Accepted Answer

1 AB : 1 Ab : 1 aB : 1 ab

Question 11

If a mutation prevents the formation of the synaptonemal complex during meiosis, which process would be most directly affected?

Accepted Answer

Crossing over between homologous chromosomes

Question 12

Which protein is primarily responsible for holding sister chromatids together until anaphase, and what happens to it at the onset of anaphase?

Accepted Answer

Cohesin; it is cleaved by separase at anaphase.

Question 13

Which of the following best describes the role of polar microtubules during mitosis?

Accepted Answer

They extend toward the opposite pole and contribute to cell elongation.

Question 14

A patient is diagnosed with a cancer characterized by uncontrolled cell division. Which of the following is most likely defective in these cells?

Accepted Answer

Cell cycle checkpoints

Question 15

During which stage of meiosis do homologous chromosomes separate, and what is the resulting chromosome number in each daughter cell?

Accepted Answer

Anaphase I; each daughter cell is haploid ($$n).$$

Question 16

Which of the following statements about the pseudoautosomal regions (PARs) of the X and Y chromosomes is correct?

Accepted Answer

PARs are regions where X and Y chromosomes pair and undergo crossing over during meiosis.

Question 17

Which of the following best explains the mechanical basis for Mendel’s law of segregation?

Accepted Answer

Separation of homologous chromosomes during meiosis I.

Question 18

A cell is arrested at the $$G_2$$ checkpoint. Which of the following is the most likely reason for this arrest?

Accepted Answer

DNA replication is incomplete or damaged DNA has not been repaired.

Question 19

Which of the following is a real-world example of the consequences of errors in chromosome segregation during meiosis?

Accepted Answer

Down syndrome, caused by nondisjunction of chromosome 21.

Cell Division and Chromosome Heredity: Mitosis and Meiosis

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