Question 1

Use the following information to answer the questions below.
The lettered circle in the figure below shows a diploid nucleus with four chromosomes.There are two pairs of homologous chromosomes,one long and the other short.One haploid set is symbolized as black and the other haploid set is grey.The chromosomes in the unlettered circle have not yet replicated.Choose the correct chromosomal conditions for the following stages.
 
-What is the correct chromosomal condition at the prometaphase of mitosis?

Accepted Answer

The answer of Use the following information to answer the...

Question 2

Exposure of zebrafish nuclei to meiotic cytosol resulted in phosphorylation of NEP55 and L68 proteins by cyclin-dependent kinase 2.NEP55 is a protein of the inner nuclear membrane,and L68 is a protein of the nuclear lamina.What is the most likely role of phosphorylation of these proteins in the process of mitosis?

Accepted Answer

Phosphorylation of NEP55 and L68 proteins is likely involved in the disassembly of the nuclear envelope during mitosis. NEP55 is a protein of the inner nuclear membrane, while L68 is a protein of the nuclear lamina. The nuclear envelope must break down to allow the spindle microtubules to access the chromosomes and facilitate their separation during mitosis. Phosphorylation of these proteins is likely to be involved in this process.

Question 3

At the M phase checkpoint,the complex allows for what to occur?

Accepted Answer

At the M phase checkpoint, the complex allows for separase enzyme to cleave cohesins and allows chromatids to separate. This separation of chromatids ensures that each daughter cell receives the correct number of chromosomes during cell division.

Question 4

The following questions are based on the following figure.
 
-G₁ is represented by which numbered part(s)of the cycle?

Accepted Answer

The answer of The following questions are based on the...

Question 5

All cell cycle checkpoints are similar in which way?

Accepted Answer

All cell cycle checkpoints activate or inactivate other proteins, such as tumor suppressor proteins and DNA repair enzymes, in order to ensure proper cell cycle progression and prevent damaged or abnormal cells from dividing. The other statements are not true for all checkpoints. For example, different checkpoints respond to different cyclins and utilize different Cdks. Additionally, not all checkpoints give the go-ahead signal to progress to the next checkpoint.

Question 6

Besides the ability of some cancer cells to overproliferate,what else could logically result in a tumour?

Accepted Answer

The answer of Besides the ability of some cancer cells...

Question 7

Only once all kinetochores are attached to spindle microtubules can ________ proceed.

Accepted Answer

Anaphase cannot occur until all kinetochores are attached to spindle microtubules. This ensures that each chromosome will be properly segregated to each daughter cell. Metaphase can begin once the chromosomes have aligned at the metaphase plate, but anaphase cannot begin until all kinetochores are attached. Synthesis (DNA replication) and G₀ are not part of the mitotic process. MPF, or the mitotic checkpoint complex, is responsible for ensuring that all kinetochores are properly attached before allowing anaphase to proceed.

Question 8

After which checkpoint is the cell first committed to continue the cell cycle through M?

Accepted Answer

The checkpoint at G1 is the point at which the cell is first committed to continue through the cell cycle to M phase. At this checkpoint, the cell checks for damage to DNA before deciding whether to move on to the S phase. If the DNA is damaged beyond repair, the cell may enter a quiescent state (G0) or undergo apoptosis. Once the DNA is deemed intact, the cell is committed to continue through the cell cycle to M phase.

Question 9

Use the following information to answer the questions below.
The lettered circle in the figure below shows a diploid nucleus with four chromosomes.There are two pairs of homologous chromosomes,one long and the other short.One haploid set is symbolized as black and the other haploid set is grey.The chromosomes in the unlettered circle have not yet replicated.Choose the correct chromosomal conditions for the following stages.
 
-What is the correct chromosomal condition for one daughter nucleus at telophase of mitosis?

Accepted Answer

The answer of Use the following information to answer the...

Question 10

Which of the following most accurately describes a cyclin?

Accepted Answer

Cyclins activate a cyclin-dependent kinase (Cdk) molecule when they are present in sufficient concentrations. This activation triggers the progression of the cell cycle. Cyclins are not present in similar concentrations throughout the cell cycle and their concentration does not decrease when MPF activity increases. Cyclins complex with a Cdk to activate it, not phosphorylate it.

Question 11

For a chemotherapeutic drug to be useful for treating cancer cells,which of the following is most desirable?

Accepted Answer

Chemotherapeutic drugs that interfere with rapidly dividing cells are desirable because cancer cells often divide rapidly. By targeting these cells, the drugs can selectively kill cancer cells while sparing normal, healthy cells that divide more slowly.

Question 12

Why do neurons and some other specialized cells divide infrequently?

Accepted Answer

Cells that have been shunted into G₀ are in a quiescent state and are no longer actively dividing. Neurons and some other specialized cells, such as muscle cells, have entered this stage and do not divide frequently.

Question 13

The following questions are based on the following figure.
 
-Which number represents DNA synthesis?

Accepted Answer

Number II represents DNA synthesis, as it is the step where new strands of DNA are synthesized by DNA polymerase.

Question 14

The following questions are based on the following figure.
 
-In the figure above,mitosis is represented by which numbered part(s)of the cycle?

Accepted Answer

The answer of The following questions are based on the...

Question 15

A research team began a study of a cultured cell line.Their preliminary observations showed them that the cell line did not exhibit either density-dependent inhibition or anchorage dependence.What could they conclude right away?

Accepted Answer

The lack of density-dependent inhibition and anchorage dependence are both hallmarks of tumor cells. Therefore, the researchers can conclude that the cell line shows characteristics of tumors.

Question 16

Density-dependent inhibition depends on the binding of a cell-surface protein to its counterpart on an adjoining cell's surface.A growth inhibiting signal is sent to both cells,preventing them from dividing.Certain external physical factors can affect this inhibition mechanism.Select the statement that makes a correct prediction about natural phenomena that could occur during the cell cycle to prevent cell growth.

Accepted Answer

Density-dependent inhibition relies on the availability of growth factors and nutrients. As cells become more numerous, the amount of resources available per cell becomes limited, preventing further cell growth. A and B do not accurately reflect the mechanism of density-dependent inhibition, and D and E are incorrect predictions that have no basis in the described process.

Question 17

-If the cell whose nuclear material is shown in the figure above continues toward completion of mitosis,which of the following events would occur next?

Accepted Answer

The answer of 
-If the cell whose nuclear material is...

Question 18

You observe cells under the microscope and notice that,as they undergo mitosis,the nucleus remains intact.You conclude that these cells are

Accepted Answer

The answer of You observe cells under the microscope and...

Question 19

The following questions are based on the following figure.
 
-Which number represents the point in the cell cycle during which the chromosomes are replicated?

Accepted Answer

Phase II represents the S (synthesis) phase of the cell cycle, during which DNA replication occurs.

Question 20

Successfully growing cells in a culture requires the researcher to understand

Accepted Answer

Anchorage dependence is the requirement for cells to attach to a surface in order to grow and divide. This is a critical factor in cell culture, as cells that are not anchorage-dependent will not grow in a monolayer and will instead form clumps or aggregates.

Quiz 12: The Cell Cycle