Question 1

A group of cells is assayed for DNA content immediately following mitosis and is found to have an average of 8 picograms of DNA per nucleus.How many picograms would be found at the end of S and the end of G₂?

Accepted Answer

At the end of S phase, the amount of DNA in each nucleus doubles, so there would be an average of 16 picograms of DNA per nucleus. At the end of G2 phase, the amount of DNA remains the same as in the S phase, so there would still be an average of 16 picograms of DNA per nucleus. Therefore, the correct answer is D (16; 16).

Question 2

The centromere is a region in which

Accepted Answer

The centromere is a specialized region on a chromosome where the two sister chromatids are held together. This attachment is necessary for the proper alignment and separation of chromosomes during cell division. The centromere is responsible for keeping chromatids together until anaphase when the sister chromatids are separated and pulled to opposite poles of the cell.

Question 3

Which of the following best describes how chromosomes move toward the poles of the spindle during mitosis?

Accepted Answer

D

Question 4

During which phase of mitosis do the chromatids become chromosomes?

Accepted Answer

During telophase, the chromatids that were pulled apart during anaphase reach the opposite poles of the cell and de-condense, forming two new nuclei. At this point, each chromatid is considered a separate chromosome, marking the end of mitosis and leading into cytokinesis.

Question 5

Suppose a biologist can separate one of a dozen pieces of chromatin from a eukaryotic (animal)nucleus.It might consist of which of the following?

Accepted Answer

Chromatin is composed of long strands of DNA that are coiled around proteins called histones, forming a nucleosome. Therefore, one piece of chromatin would consist of two long strands of DNA plus associated proteins. Choices A, B, and C are incorrect as they do not accurately reflect what a piece of chromatin would consist of. Choice E is also incorrect as it refers to a duplicated chromosome, rather than a single piece of chromatin.

Question 6

Why do chromosomes coil during mitosis?

Accepted Answer

Chromosomes coil during mitosis to become more compact, which helps prevent them from becoming entangled and breaking as they are separated into daughter cells. This compact structure facilitates their movement and ensures accurate distribution to each daughter cell.

Question 7

For a newly evolving protist,what would be the advantage of using eukaryote-like cell division rather than prokaryotic binary fission?

Accepted Answer

Using eukaryotic cell division would allow for the orderly and efficient segregation of multiple linear chromosomes, which is necessary for maintaining genetic stability and preventing errors during cell division. Prokaryotic binary fission, on the other hand, only replicates one circular chromosome and can lead to errors in segregation.

Question 8

At which phase are centrioles beginning to move apart in animal cells?

Accepted Answer

During prophase of mitosis, the centrioles begin to move apart and start to form spindle fibers.

Question 9

For anaphase to begin,which of the following must occur?

Accepted Answer

Cohesin must be cleaved enzymatically for sister chromatids to separate and move to opposite poles, which is the hallmark of anaphase.

Question 10

If there are 20 chromatids in a cell,how many centromeres are there?

Accepted Answer

Each pair of sister chromatids has one centromere, so if there are 20 chromatids, there must be 10 centromeres.

Question 11

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?

Accepted Answer

The answer of Measurements of the amount of DNA per...

Question 12

In which group of eukaryotic organisms does the nuclear envelope remain intact during mitosis?

Accepted Answer

The answer of In which group of eukaryotic organisms does...

Question 13

Which of the following are primarily responsible for cytokinesis in plant cells but not in animal cells?

Accepted Answer

In plant cells, cytokinesis occurs through the formation of a cell plate, which is created by the fusion of Golgi-derived vesicles at the center of the cell. This process is not observed in animal cells, so Golgi-derived vesicles are primarily responsible for cytokinesis in plant cells. Kinetochores, actin and myosin, centrioles and centromeres, and cyclin-dependent kinases are not exclusive to cytokinesis in plant cells.

Question 14

Where do the microtubules of the spindle originate during mitosis in both plant and animal cells?

Accepted Answer

The microtubules of the spindle originate from the centrosome, which duplicates and then separates during mitosis in both plant and animal cells. Centrioles are a component of the centrosome, but not all cells have centrioles, and even those that do can still form a spindle without them. Centromeres and kinetochores are attachment points for the spindle, but they do not originate the microtubules themselves. Chromatids are individual strands of DNA that are pulled apart by the spindle during mitosis.

Question 15

Movement of the chromosomes during anaphase would be most affected by a drug that

Accepted Answer

During anaphase, chromosomes are pulled apart to opposite poles of the cell. This movement is facilitated by the shortening of microtubules. A drug that prevents the shortening of microtubules would directly interfere with this process, thus most affecting the movement of chromosomes during anaphase.

Question 16

Which of the following is a function of those spindle microtubules that do not attach to kinetochores?

Accepted Answer

The spindle microtubules that do not attach to kinetochores are responsible for maintaining the region of overlap of microtubules in the cell's center, which is necessary for the stability and integrity of the spindle apparatus. This function is critical for proper chromosome alignment and segregation during cell division.

Question 17

If there are 20 centromeres in a cell at anaphase,how many chromosomes are there in each daughter cell following cytokinesis?

Accepted Answer

The answer of If there are 20 centromeres in a...

Question 18

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

Accepted Answer

Each cell division doubles the number of cells. Starting from a single cell (the zygote), after five divisions, the cell count would be 2^5 = 32.

Question 19

Taxol is an anticancer drug extracted from the Pacific yew tree.In animal cells,Taxol disrupts microtubule formation by binding to microtubules and accelerating their assembly from the protein precursor,tubulin.Surprisingly,this stops mitosis.Specifically,Taxol must affect

Accepted Answer

Taxol disrupts microtubule formation, which is responsible for the formation of the mitotic spindle. Without a properly formed spindle, mitosis cannot occur. Therefore, choice A is the correct answer. Choices B, C, D, and E are incorrect because Taxol does not directly affect anaphase, formation of centrioles, chromatid assembly, or the S phase of the cell cycle.

Question 20

If cells in the process of dividing are subjected to colchicine,a drug that interferes with the formation of the spindle apparatus,at which stage will mitosis be arrested?

Accepted Answer

Colchicine interferes with the formation of the spindle apparatus, which is responsible for separating sister chromatids during mitosis. Therefore, if cells in the process of dividing are exposed to colchicine, mitosis will be arrested in metaphase, as this is the stage where chromosomes are aligned on the spindle apparatus before they are separated into two daughter cells.

Quiz 12: The Cell Cycle