Question 1

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

Accepted Answer

DNA replication occurs during the S phase, resulting in each chromosome having two chromatids.

Question 2

Which protein is responsible for holding sister chromatids together, and which enzyme cleaves this protein to allow chromatid separation during anaphase?

Accepted Answer

Cohesin holds sister chromatids together, and separase cleaves cohesin during anaphase.

Question 3

A mutation causes a cell to skip the metaphase checkpoint. What is the most likely consequence of this mutation?

Accepted Answer

Chromosomes may not be properly attached to spindle fibers, leading to aneuploidy.

Question 4

Which of the following best describes the difference between mitosis and meiosis in terms of genetic diversity?

Accepted Answer

Mitosis produces genetically identical cells, while meiosis increases genetic diversity through crossing over and independent assortment.

Question 5

If a human somatic cell has 46 chromosomes at the start of G1, how many chromatids will be present in the cell at the end of S phase?

Accepted Answer

92 chromatids

Question 6

Which structure is responsible for organizing spindle fibers and defining the poles of the cell during mitosis?

Accepted Answer

Centrosome

Question 7

During which stage of mitosis do chromosomes align at the cell's equatorial plane, and what is the significance of this alignment?

Accepted Answer

Metaphase; it ensures that each daughter cell will receive one copy of each chromosome.

Question 8

A plant cell is observed forming a new cell wall at the midline during cytokinesis. What is this structure called, and how does it differ from cytokinesis in animal cells?

Accepted Answer

Cell plate; animal cells form a cleavage furrow instead.

Question 9

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

Accepted Answer

Metaphase checkpoint

Question 10

In meiosis, what is the genetic significance of crossing over during prophase I?

Accepted Answer

It increases genetic diversity by exchanging genetic material between nonsister chromatids.

Question 11

A cell is observed with chromosomes condensed, the nuclear envelope breaking down, and spindle fibers beginning to form. Which stage of mitosis is this cell in?

Accepted Answer

Prophase

Question 12

Which of the following equations correctly represents the reduction in chromosome number during meiosis?

Accepted Answer

$$2n \rightarrow n$$

Question 13

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

Accepted Answer

Synapsis and crossing over between homologous chromosomes

Question 14

Which law of Mendelian genetics is explained by the separation of homologous chromosomes during meiosis I?

Accepted Answer

Law of Segregation

Question 15

A male human's X and Y chromosomes pair during meiosis due to which specific regions?

Accepted Answer

Pseudoautosomal regions (PAR1 and PAR2)

Question 16

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

Accepted Answer

They stabilize the spindle and help elongate the cell during division.

Question 17

A cell with a defective separase enzyme would most likely fail at which step of mitosis?

Accepted Answer

Anaphase, because sister chromatids would not separate.

Question 18

Which phase of the cell cycle is characterized by high gene expression and cell growth, but not DNA replication?

Accepted Answer

G1 phase

Question 19

If a cell remains specialized and does not divide, which phase of the cell cycle is it most likely in?

Accepted Answer

G0 phase

Question 20

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

Accepted Answer

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

Cell Division and Chromosome Heredity: Mitosis and Meiosis

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