Question 1

Eukaryotic chromosomes are composed of which of the following macromolecules?
A) DNA and RNA
B) DNA only
C) DNA and proteins
D) DNA and phospholipids

Accepted Answer

Eukaryotic chromosomes are composed of DNA and proteins called histones. The DNA wraps around the histone proteins to form nucleosomes, which further condense into chromatin fibers and eventually into chromosomes. RNA may be present in some regions of the chromosome, but it is not a major component of the chromosome structure. Phospholipids are not found in chromosomes.

Question 2

Starting with a fertilised egg (zygote), a series of six cell divisions would produce an early embryo with how many cells?
A) 12
B) 16
C) 32
D) 64

Accepted Answer

Each cell division doubles the number of cells, so after six divisions, the zygote will have 2^6 = 64 cells.

Question 3

Certain cell types normally have several nuclei per cell. How could such multinucleated cells be explained?
A) The cell underwent repeated cytokinesis but not mitosis.
B) The cell underwent repeated mitosis with simultaneous cytokinesis.
C) The cell underwent repeated mitosis, but cytokinesis did not occur.
D) The cell had multiple S phases before it entered mitosis.

Accepted Answer

Multinucleated cells can result from repeated mitosis without cytokinesis, leading to multiple nuclei within a single cell.

Question 4

In a diploid cell with 5 chromosome pairs (2n = 10), how many sister chromatids will be found in a nucleus at prophase of mitosis?
A) 5
B) 10
C) 20
D) 40

Accepted Answer

At prophase of mitosis, each chromosome consists of two sister chromatids. Therefore, in a diploid cell with 5 chromosome pairs (10 chromosomes total), there will be 20 sister chromatids at prophase of mitosis.

Question 5

In what way do kinetochore microtubules facilitate the process of splitting the centromeres?
A) They use motor proteins to hydrolyse the centromere at specific arginine residues.
B) They create tension by pulling toward opposite poles.
C) They slide past each other like actin microfilaments.
D) They phosphorylate the centromere, thereby changing its conformation.

Accepted Answer

Kinetochore microtubules attach to the kinetochore proteins on the centromere of each chromosome and pull in opposite directions, creating tension that facilitates the splitting of the sister chromatids at the centromere. This is known as the process of anaphase. Option A is incorrect as motor proteins do not hydrolyze the centromere, and option C is also incorrect as kinetochore microtubules do not slide past each other. Option D is also incorrect as there is no evidence that kinetochore microtubules phosphorylate the centromere.

Question 6

In the cells of many eukaryotic species, the nuclear envelope has to disappear to permit which of the following events in the cell cycle?
A) DNA synthesis
B) attachment of microtubules to kinetochores
C) separation of the centrosomes
D) condensation of the chromosomes

Accepted Answer

The attachment of microtubules to kinetochores, which occurs during mitosis, requires the disappearance of the nuclear envelope. This allows the microtubules to access the chromosomes and pull them apart towards the opposite poles of the cell. The other events listed (DNA synthesis, separation of the centrosomes, and condensation of the chromosomes) do not require the disappearance of the nuclear envelope.

Question 7

In a diploid cell with 5 chromosome pairs (2n = 10), how many centromeres will be found in a nucleus at G2 of the cell division cycle?
A) 5
B) 10
C) 20
D) 40

Accepted Answer

The answer of In a diploid cell with 5 chromosome...

Question 8

Measurements of the amount of DNA per nucleus were taken on a large number of cells from a growing fungus. The measured DNA levels ranged from 3 to 6 picograms per nucleus. In which stage of the cell cycle did the nucleus contain 6 picograms of DNA?
A) G1
B) S
C) G2
D) G0

Accepted Answer

During the G2 phase, the DNA content is doubled compared to the G1 phase, as DNA replication occurs during the S phase. Therefore, a nucleus with 6 picograms of DNA is in the G2 phase.

Question 9

How is plant cell cytokinesis different from animal cell cytokinesis?
A) The contractile filaments found in plant cells are structures composed of carbohydrates; the cleavage furrow in animal cells is composed of contractile proteins.
B) Plant cells deposit vesicles containing cell wall building blocks on the metaphase plate; animal cells form a cleavage furrow.
C) The structural proteins of plant cells separate the two cells; in animal cells, a cell membrane separates the two daughter cells.
D) Plant cells divide after metaphase but before anaphase; animal cells divide after anaphase.

Accepted Answer

During cell division in plant cells, vesicles containing cell wall building blocks are deposited on the metaphase plate to form a cell plate, which eventually becomes the new cell wall between the two daughter cells. In contrast, animal cells form a cleavage furrow, a contractile ring that pinches the cell in two.

Question 10

Scientists isolate cells in various phases of the cell cycle. They isolate a group of cells that have 1½ times more DNA than G1 phase cells. What is the most likely part of the cell cycle from which these cells were isolated?
A) between the G1 and S phases in the cell cycle
B) in the G2 phase of the cell cycle
C) in the M phase of the cell cycle
D) in the S phase of the cell cycle

Accepted Answer

Cells in the S phase have duplicated their DNA, resulting in double the amount of DNA as G1 phase cells. Therefore, cells with 1½ times more DNA than G1 phase cells are likely in the middle of the S phase, just before the completion of DNA replication.

Question 11

If there are 40 centromeres in a cell at anaphase of mitosis, how many chromosomes will be found in each daughter cell following cytokinesis?
A) 10
B) 20
C) 40
D) 80

Accepted Answer

At anaphase of mitosis, the sister chromatids separate and become individual chromosomes, each with one centromere. Therefore, if there are 40 centromeres in the cell, there are 40 chromosomes. After cytokinesis, the two daughter cells will have an equal number of chromosomes, which is 40/2 = 20 chromosomes in each daughter cell. Option B is the only option with 20 chromosomes.

Question 12

Taxol is an anticancer drug extracted from the Pacific yew tree. In animal cells, Taxol prevents microtubule depolymerisation. Thus, Taxol stops mitosis by interfering with which of the following structures or processes?
A) the mitotic spindle
B) cytokinesis
C) centriole duplication
D) chromosome condensation

Accepted Answer

Taxol prevents microtubule depolymerisation, which interferes with the formation and function of the mitotic spindle. The mitotic spindle is responsible for separating chromosomes during mitosis, and without a functional spindle, mitosis cannot proceed properly. Taxol does not directly affect cytokinesis, centriole duplication, or chromosome condensation.

Question 13

Movement of the chromosomes during anaphase would be most affected by a drug that prevents which of the following events in mitosis and cell division?
A) nuclear envelope breakdown
B) elongation of microtubules
C) shortening of microtubules
D) formation of a cleavage furrow

Accepted Answer

During anaphase, the chromosomes are pulled apart by the shortening of the microtubules connecting them to the spindle fibers. Therefore, a drug that prevents the shortening of microtubules would prevent the movement of the chromosomes during anaphase.

Question 14

The mitotic spindle plays a critical role in which of the following processes?
A) splitting of the cell (cytokinesis) following mitosis
B) triggering the compaction and condensation of chromosomes
C) dissolving the nuclear membrane
D) separation of sister chromatids

Accepted Answer

The mitotic spindle is responsible for aligning and separating sister chromatids during mitosis. It does not play a role in cytokinesis, compaction/condensation of chromosomes, or dissolving the nuclear membrane.

Question 15

What is the name of the microtubule-organising centre found in animal cells as an identifiable structure present during all phases of the cell cycle?
A) centriole
B) centrosome
C) centromere
D) kinetochore

Accepted Answer

The centrosome is the microtubule-organising centre found in animal cells, which is present during all phases of the cell cycle. The centriole is a component of the centrosome, but not the entire organelle. The centromere is a region of DNA that binds to spindle fibres during cell division, and the kinetochore is the protein structure that forms on the centromere and attaches to spindle fibres.

Question 16

Metaphase is characterised by ________.
A) alignment of chromosomes on the equator of the cell
B) separation of the centromeres
C) cytokinesis
D) separation of sister chromatids

Accepted Answer

Metaphase is the stage of mitosis in which the chromosomes line up on the equator of the cell, also known as the metaphase plate. This alignment is necessary for the proper separation of chromosomes during anaphase. The separation of centromeres and sister chromatids occurs during anaphase and not during metaphase. Cytokinesis, which is the division of the cytoplasm to form two daughter cells, occurs after mitosis is complete.

Question 17

G1 is associated with which of the following cellular events?
A) normal growth and cell function
B) DNA replication
C) the beginning of mitosis
D) break down of the nuclear membrane

Accepted Answer

G1 phase is the first gap phase of the cell cycle, during which the cell grows, carries out normal cellular functions, and prepares for DNA replication in the S phase. Therefore, G1 phase is associated with normal growth and cell function.

Question 18

FtsZ is a bacterial cytoskeletal protein that forms a contractile ring involved in binary fission. Its function is analogous to ________.
A) the cleavage furrow of eukaryotic animal cells
B) the cell plate of eukaryotic plant cells
C) the mitotic spindle of eukaryotic cells
D) the microtubule-organising centre of eukaryotic cells

Accepted Answer

FtsZ is involved in binary fission, which is the process of bacterial cell division. During this process, FtsZ forms a contractile ring at the site of cell division, which determines the plane of division and eventually leads to the formation of two daughter cells. This function is analogous to the cleavage furrow of eukaryotic animal cells, which also forms a contractile ring during cell division to separate daughter cells. The other options (B, C, and D) are not as closely related to the function of FtsZ in bacterial cell division.

Question 19

If a cell at metaphase of mitosis contains 20 sister chromatids, how many chromosomes will be present in a G1 cell?
A) 5
B) 10
C) 20
D) 40

Accepted Answer

During metaphase of mitosis, the cell contains 20 sister chromatids, which means that there are 10 chromosomes (since each chromosome is composed of 2 sister chromatids). Therefore, in a G1 cell, which only contains one copy of each chromosome, there will be 10 chromosomes.

Question 20

At which phase of the cell cycle do centrioles begin to move apart in animal cells?
A) anaphase
B) telophase
C) metaphase
D) prophase

Accepted Answer

Centrioles begin to move apart during prophase of animal cell division. During this phase, the chromatin condenses into distinct chromosomes and the spindle apparatus begins to form. The two centrioles move to opposite poles of the cell and begin to form spindle fibers.

Quiz 12: The Cell Cycle

Eukaryotic chromosomes are composed of which of the following macromolecules?

Starting with a fertilised egg (zygote) , a series of six cell divisions would produce an early embryo with how many cells?

Certain cell types normally have several nuclei per cell. How could such multinucleated cells be explained?

In a diploid cell with 5 chromosome pairs (2n = 10) , how many sister chromatids will be found in a nucleus at prophase of mitosis?

In what way do kinetochore microtubules facilitate the process of splitting the centromeres?

In the cells of many eukaryotic species, the nuclear envelope has to disappear to permit which of the following events in the cell cycle?

In a diploid cell with 5 chromosome pairs (2n = 10) , how many centromeres will be found in a nucleus at G2 of the cell division cycle?

Measurements of the amount of DNA per nucleus were taken on a large number of cells from a growing fungus. The measured DNA levels ranged from 3 to 6 picograms per nucleus. In which stage of the cell cycle did the nucleus contain 6 picograms of DNA?

How is plant cell cytokinesis different from animal cell cytokinesis?

Scientists isolate cells in various phases of the cell cycle. They isolate a group of cells that have 1½ times more DNA than G1 phase cells. What is the most likely part of the cell cycle from which these cells were isolated?

If there are 40 centromeres in a cell at anaphase of mitosis, how many chromosomes will be found in each daughter cell following cytokinesis?

Taxol is an anticancer drug extracted from the Pacific yew tree. In animal cells, Taxol prevents microtubule depolymerisation. Thus, Taxol stops mitosis by interfering with which of the following structures or processes?

Movement of the chromosomes during anaphase would be most affected by a drug that prevents which of the following events in mitosis and cell division?

The mitotic spindle plays a critical role in which of the following processes?

What is the name of the microtubule-organising centre found in animal cells as an identifiable structure present during all phases of the cell cycle?

Metaphase is characterised by ________.

G1 is associated with which of the following cellular events?

FtsZ is a bacterial cytoskeletal protein that forms a contractile ring involved in binary fission. Its function is analogous to ________.

If a cell at metaphase of mitosis contains 20 sister chromatids, how many chromosomes will be present in a G1 cell?

At which phase of the cell cycle do centrioles begin to move apart in animal cells?