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Chapter 12: Q4TYU (page 234)

The decline of MPF activity at the end of mitosis is due to

(A) the destruction of the protein kinase CDK.

(B) decreased synthesis of Cdk.

(C) degradation of cyclin

(D) accumulation of cyclin.

Short Answer

Expert verified

(A) The option “the destruction of the protein kinase CDK” is false.

(B) The option “decreased synthesis of Cdk” is false.

(C) The option “degradation of cyclin” is true.

(D) The option “accumulation of cyclin” is false.

Step by step solution

01

Description of cell division

Every organism tends to grow depending upon the available favorable factors. The growth occurs due to the process of cell division, such as mitosis and meiosis. Mitosis takes place in the normal cells. Meiosis occurs in the gametes.

02

Explanation of option (A)        

Protein kinase CDK is the kinase that regulates the transcription mechanism. It also controls the cell division process.

The maturation promotion factors are not related to the protein kinases.

Therefore, the given statement is false.

03

Explanation of option (B)

The cyclin-dependent kinases are the protein kinases that are involved in mitosis. These kinases get attached to the cyclin molecules to get activated.

The maturation promoting factor is not dependent on the cdks alone. So, the decline in the MPF does not take place only with the decreased production of cdks.

Therefore, the given statement is false.

04

Explanation of option (C)

The mitosis promoting factor has kinase activity. In order to perform the kinase activity, there is a need for cyclins. Cycling is the regulatory protein for the cell cycle progression.

The degradation of cyclin can, in turn, lead to a decline in MPF at the mitosis.

Therefore, the given statement is true.

05

Explanation of option (D)

Accumulation of cyclin tends to increase the kinase activity of mitosis promoting factor. It does not cause a decline in the MPF.

The accumulation of cyclin can increase the activity of mitosis-promoting factors.

Therefore, the given statement is false

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Most popular questions from this chapter

One difference between cancer cells and normal cells is that cancer cells

(A) are unable to synthesize DNA.

(B) are arrested at the S phase of the cell cycle.

(C) continue to divide even when they are tightly packed together.

(D) cannot function properly because they are affected by density-dependent inhibition.

In the cells of some organisms, mitosis occurs without cytokinesis. This will result in

(A) cells with more than one nucleus.

(B) cells that are unusually small.

(C) cells lacking nuclei.

(D) cell cycles lacking an S phase

Shown here are two HeLa cancer cells that are just completing cytokinesis. Explain how the cell division of cancer cells like these is misregulated. Identify genetic and other changes that might have caused these cells to escape normal cell cycle regulation.

Although both ends of a microtubule can gain or lose subunits, one end (called the plus end) polymerizes and depolymerizes at a higher rate than the other end (the minus end). For spindle microtubules, the plus ends are in the center of the spindle, and the minus ends are at the poles. Motor proteins that move along microtubules specialize in walking either toward the plus end-directed and minus end-directed motor proteins, respectively. Given what you know about chromosome movement and spindle changes during anaphase, predict which type of motor proteins would be present on (a) kinetochore microtubules and (b) non-kinetochore microtubules.

The histogram representing the treated sample shows the effect of growing the cancer cells alongside human umbilical cord stem cells that produce the potential inhibitor. (a) Label the histogram with the cell cycle phases. Which phase of the cell cycle has the greatest number of cells in the treated sample? Explain. (b) Compare the distribution of cells among G1, S, and G2 phases in the control and treated samples. What does this tell you about the cells in the treated sample? (c) Based on what you learned in Concept 12.3, propose a mechanism by which the stem cell-derived inhibitor might arrest the cancer cell cycle at this stage. (More than one answer is possible.)
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