Question

What would most likely be interfered with if cyclin B did not function correctly?

• A. Entry into the mitosis stage of the cell cycle
• B. Formation of microtubules
• C. Separation of chromosomes
• D. Activation of apoptosis
• E. Unscheduled entry into the G${}_2$ phase

Answer 1

The correct option is A Entry into the mitosis stage of the cell cycle

The cell cycle is controlled by the enzymes like cyclin dependent kinases or CDKs. The CDKs phosphorylate amino acids like serine and threonine which initiate or block the activities related to cell cycle. The other checkpoints involved in cell cycle regulation are:

(i) G1 checkpoint at G1/S boundary regulated by Cdk4/Cyclin D, Cdk6/ cyclin D, etc.

(ii) G2 checkpoint at G2/M boundary regulated by Cdk2/ cyclin B also known as MPF or M-phase promoting factor.

(iii) Metaphase checkpoint at Metaphase/Anaphase boundary regulated by cyclin B degradation.

Hence, if cyclin B will not function properly, the cell will not enter into M-phase i.e. Mitosis stage.

So, the correct answer is 'Entry into the mitosis stage of the cell cycle'.