Q. 18 - Biology

Question

If the M checkpoint is not cleared, what stage of mitosis will be blocked?

a.    prophase

b.    prometaphase

c.    metaphase

d.    anaphase

Step-by-Step Solution

Answer

If the M checkpoint is not cleared, the anaphase stage of mitosis will be blocked. The correct option is (d). 

Step 1. Introduction

The M checkpoint arises towards the conclusion of the metaphase stage.

Step 2. Explanation for Correct Answer

Checkpoint M is used to ensure that each of the spindle microtubules is properly linked to the spindle chromosomes of the cell. A cell's division cycle can't continue until each pair of the sister chromatids' kinetochores is securely attached to at least two spindle fibres that emerge from opposite ends of the cell's poles, a process known as anaphase.

Thus, the correct option is - (d).

Step 3. Explanation for Incorrect Answers

The M checkpoint involved sister chromatid and kinetochore, more precisely their firm association which was actually seen in anaphase. So, there is a relation between the M phase and prophase.

Thus, option (a) is incorrect.

The M checkpoint involved sister chromatid and kinetochore, more precisely their firm association which was actually seen in anaphase. So, there is a relation between the M phase and prometaphase.

Thus, option (b) is incorrect.

The M checkpoint involved sister chromatid and kinetochore, more precisely their firm association which was actually seen in anaphase. So, there is a relation between the M phase and metaphase.

Thus, option (c) is incorrect.