Question 1

What is one of the roles of the APC/C during anaphase?

Accepted Answer

The Anaphase-Promoting Complex or Cyclosome (APC/C) is a crucial cell cycle regulator that targets mitotic cyclins for destruction, thereby allowing the cell to exit mitosis. This process is essential for the progression of the cell cycle into the next phase.

Question 2

You are studying cell cycle progression in yeast cells.If you could prevent cdc2 from associating with the mitotic cyclin, the cells would:

Accepted Answer

Cdc2 is a key protein kinase that, when associated with mitotic cyclin, forms the maturation-promoting factor (MPF) necessary for the transition from G2 phase to mitosis. Preventing this association would halt the cell cycle in G2 phase.

Question 3

Plant cells typically achieve cytokinesis by:

Accepted Answer

Plant cells achieve cytokinesis by forming a cell plate across the middle of the cell, which eventually develops into a new cell wall separating the two daughter cells.

Question 4

You are leading a team of researchers at a pharmaceutical company.Your goal is to design drugs that help fight cancer.Specifically, you want to focus on drugs that bind to and inactivate certain proteins, thereby halting cell cycle progression.One of your team members suggests targeting the retinoblastoma (Rb) protein and inhibiting this protein.Will this approach be successful? Why or why not?

Accepted Answer

Inactivating the Rb protein would release the inhibition of cell cycle regulatory proteins, thereby promoting cell cycle progression, rather than halting it.

Question 5

You are studying cell cycle progression in an early frog embryo.If you were to inject a protein synthesis inhibitor into a cell during S phase, where do you predict that the cells would arrest?

Accepted Answer

The most likely point of arrest in the cell cycle after protein synthesis inhibition during S-phase would be at the G2/M checkpoint (represented by the option G₂). This is because S-phase is followed by G2-phase, during which the cell undergoes further growth and replication of organelles and prepares for mitosis. At the G2/M checkpoint, the cell checks for proper DNA replication and damage before entering into mitosis. Without proper protein synthesis during S-phase, the cell may not be able to progress into G2-phase or pass the G2/M checkpoint. Arresting at metaphase (option C) or telophase (option D) would only occur if the cell somehow managed to overcome the G2/M checkpoint and enter into mitosis.

Question 6

You are conducting a genetic screen using Caenorhabditis elegans embryos to isolate mutations affecting anaphase (A).Therefore, you need to look for embryos in which

Accepted Answer

Anaphase is the stage of mitosis when the sister chromatids are separated and move towards opposite poles of the cell. Therefore, mutations affecting anaphase are likely to disrupt this process and result in failures of chromatid separation. Option A is the most appropriate choice because it describes the movement of centromeres towards the poles, a critical step in chromatid separation during anaphase. The other options do not directly describe the anaphase process and are less likely to be affected by mutations specifically targeting anaphase.

Question 7

What stage of mitosis is essentially the reverse of prophase?

Accepted Answer

Telophase is essentially the reverse of prophase, as it involves the reformation of the nuclear envelope around the separated chromosomes and the de-condensation of chromatin.

Question 8

The drug Taxol, or Paclitaxel, is used to treat patients with a variety of cancers, including breast, lung and ovarian cancers.The drug works by stabilizing microtubules, and preventing their disassembly.The goal of the drug is to prevent dividing cells from being able to complete mitosis.As a result, cancerous cells can no longer divide.In a cell treated with Taxol, at what stage of mitosis will the cells arrest?

Accepted Answer

Taxol works by stabilizing microtubules, which are crucial for the formation of the mitotic spindle during cell division. By stabilizing the microtubules, they cannot disassemble, thus preventing the spindle from properly forming. This leads to arrest of the cells in metaphase, as the chromosomes cannot align properly on the spindle. Therefore, the correct choice is A) Prior to metaphase.

Question 9

In G₂, there are typically high levels of the mitotic cyclin.Why is cdc2 not active during G₂ if the mitotic cyclin is present?

Accepted Answer

Cdc2 is regulated by phosphorylation, and until it is phosphorylated, it remains inactive even in the presence of mitotic cyclin.

Question 10

The progress of the eukaryotic cell cycle is regulated primarily by what proteins?

Accepted Answer

Cyclins are a family of proteins that are responsible for regulating the progression of the eukaryotic cell cycle. They control the activity of cyclin-dependent kinases (CDKs), which are enzymes that phosphorylate target proteins to trigger specific cell cycle events. The levels of cyclins rise and fall during the different stages of the cell cycle, allowing for precise control of cell division.

Question 11

This protein or protein complex functions in the cell to stop cell division if the cell has experienced extensive DNA damage:

Accepted Answer

The protein p53 plays a critical role in preventing the formation and growth of tumors. When a cell has experienced extensive DNA damage, p53 is activated and functions to stop the cell cycle, allowing time for DNA repair mechanisms to take place. This helps prevent the accumulation of mutations that could ultimately result in the cell becoming cancerous. APC/C is involved in regulating the progression of the cell cycle, particularly in the transition from metaphase to anaphase. FtsZ is involved in bacterial cell division, and Condensin plays a role in chromatin compaction during mitosis.

Question 12

What would you expect to happen if the anaphase-promoting complex/cyclosome (APC/C) failed to ubiquitinate securin?

Accepted Answer

If APC/C fails to ubiquitinate securin, then securin will be unable to degrade separase, and the cohesin complex will persist. This will prevent the cell from entering anaphase because the chromosomes will not be able to separate.

Question 13

If a cell was capable of bypassing metaphase and going directly from prometaphase to anaphase, what is the most likely consequence of this?

Accepted Answer

Metaphase is the stage during mitosis when chromosomes align in the center of the cell, and the spindle fibers attach to the kinetochores of each chromosome. If a cell bypasses metaphase and goes directly to anaphase, the chromosomes would not be properly aligned and separated, leading to daughter cells with different numbers of chromosomes. This could potentially lead to genetic abnormalities or cell death. Option A is incorrect because the nuclear envelope breaks down during prometaphase, and it is normal for daughter cells to not have one immediately after mitosis. Option B is also incorrect because cytoplasmic materials are distributed evenly during cytokinesis, which occurs after mitosis. Option D is incorrect because bypassing metaphase would be abnormal and could have consequences for the daughter cells.

Question 14

If you were to think of the cell as a car, and mitosis as a process that drives that car to go, what would be a good analogy for a cell that has a mutation in both copies of a tumor-suppressor gene?

Accepted Answer

A mutation in both copies of a tumor-suppressor gene is like the brake pedal of a car not working at all, as it prevents the cell from stopping division, similar to a car that cannot stop without functioning brakes.

Question 15

Why is it so important that all of the chromosomes align on the metaphase plate during metaphase?

Accepted Answer

Proper alignment ensures that chromosomes are correctly attached to spindle microtubules, allowing for accurate separation during anaphase.

Question 16

You are examining the effect of maturation-promoting factor (MPF) in sea urchin cells, which have a diploid number of 36.If you fuse a dividing sea urchin cell with a G₁ arrested oocyte, what would be the outcome?

Accepted Answer

The G₁ cell, which is arrested in G1 phase, would be induced to enter mitosis by the maturation-promoting factor (MPF) from the dividing cell. However, because it has not replicated its DNA (which occurs in S phase), it would likely arrest at the spindle checkpoint due to unreplicated chromosomes, preventing proper segregation.

Question 17

Animal cells typically achieve cytokinesis by:

Accepted Answer

Animal cells achieve cytokinesis by forming a cleavage furrow, which pinches the cell into two separate daughter cells.

Question 18

At what checkpoint(s) does the cell arrest in response to DNA damage?

Accepted Answer

The cell can arrest at both the G1/S and G2/M checkpoints in response to DNA damage to allow for repair before DNA replication or mitosis.

Question 19

What time point represents G₂?

Accepted Answer

The answer of What time point represents G₂? ...

Question 20

What is separase?

Accepted Answer

Separase is a protein that plays a critical role in the separation of sister chromatids during cell division. It does so by cleaving the cohesin protein complex, which holds the sister chromatids together. The cleavage of cohesin by separase enables the separation of sister chromatids and their subsequent segregation to the daughter cells. Therefore, choice C is the best answer as it correctly describes separase's function in cleaving cohesin.

Quiz 10: How Cells Divide

What is one of the roles of the APC/C during anaphase?

You are studying cell cycle progression in yeast cells.If you could prevent cdc2 from associating with the mitotic cyclin, the cells would:

Plant cells typically achieve cytokinesis by:

You are studying cell cycle progression in an early frog embryo.If you were to inject a protein synthesis inhibitor into a cell during S phase, where do you predict that the cells would arrest?

You are conducting a genetic screen using Caenorhabditis elegans embryos to isolate mutations affecting anaphase (A) .Therefore, you need to look for embryos in which

What stage of mitosis is essentially the reverse of prophase?

In G₂, there are typically high levels of the mitotic cyclin.Why is cdc2 not active during G₂ if the mitotic cyclin is present?

The progress of the eukaryotic cell cycle is regulated primarily by what proteins?

This protein or protein complex functions in the cell to stop cell division if the cell has experienced extensive DNA damage:

What would you expect to happen if the anaphase-promoting complex/cyclosome (APC/C) failed to ubiquitinate securin?

If a cell was capable of bypassing metaphase and going directly from prometaphase to anaphase, what is the most likely consequence of this?

If you were to think of the cell as a car, and mitosis as a process that drives that car to go, what would be a good analogy for a cell that has a mutation in both copies of a tumor-suppressor gene?

Why is it so important that all of the chromosomes align on the metaphase plate during metaphase?

You are examining the effect of maturation-promoting factor (MPF) in sea urchin cells, which have a diploid number of 36.If you fuse a dividing sea urchin cell with a G₁ arrested oocyte, what would be the outcome?

Animal cells typically achieve cytokinesis by:

At what checkpoint(s) does the cell arrest in response to DNA damage?

What time point represents G₂?

What is separase?

Quiz 10: How Cells Divide

What is one of the roles of the APC/C during anaphase?

You are studying cell cycle progression in yeast cells.If you could prevent cdc2 from associating with the mitotic cyclin, the cells would:

Plant cells typically achieve cytokinesis by:

You are studying cell cycle progression in an early frog embryo.If you were to inject a protein synthesis inhibitor into a cell during S phase, where do you predict that the cells would arrest?

You are conducting a genetic screen using Caenorhabditis elegans embryos to isolate mutations affecting anaphase (A) .Therefore, you need to look for embryos in which

What stage of mitosis is essentially the reverse of prophase?

In G2, there are typically high levels of the mitotic cyclin.Why is cdc2 not active during G2 if the mitotic cyclin is present?

The progress of the eukaryotic cell cycle is regulated primarily by what proteins?

This protein or protein complex functions in the cell to stop cell division if the cell has experienced extensive DNA damage:

What would you expect to happen if the anaphase-promoting complex/cyclosome (APC/C) failed to ubiquitinate securin?

If a cell was capable of bypassing metaphase and going directly from prometaphase to anaphase, what is the most likely consequence of this?

If you were to think of the cell as a car, and mitosis as a process that drives that car to go, what would be a good analogy for a cell that has a mutation in both copies of a tumor-suppressor gene?

Why is it so important that all of the chromosomes align on the metaphase plate during metaphase?

You are examining the effect of maturation-promoting factor (MPF) in sea urchin cells, which have a diploid number of 36.If you fuse a dividing sea urchin cell with a G1 arrested oocyte, what would be the outcome?

Animal cells typically achieve cytokinesis by:

At what checkpoint(s) does the cell arrest in response to DNA damage?

What time point represents G2?

What is separase?

In G₂, there are typically high levels of the mitotic cyclin.Why is cdc2 not active during G₂ if the mitotic cyclin is present?

You are examining the effect of maturation-promoting factor (MPF) in sea urchin cells, which have a diploid number of 36.If you fuse a dividing sea urchin cell with a G₁ arrested oocyte, what would be the outcome?

What time point represents G₂?