Question

Regarding the assertion and reason; choose the correct option.

Assertion [A]: Cyclin and CDK complex constitute various checkpoints to ensure correct sequence and product in each phase of cell division .

Reason [R]: The Cyclin and CDK complex acts as molecular regulators or switches.

• A. Assertion [A] is True and Reason [R] is False.
• B. Reason [R] is True and Assertion [A] is False.
• C. Assertion [A] is True and Reason [R] is True and is a correct explanation to [A].
• D. Assertion [A] is True and Reason [R] is True but is an incorrect explanation to [A].

Answer 1

The correct option is C

Assertion [A] is True and Reason [R] is True and is a correct explanation to [A].

It was proven in 2001, that Cyclin and CDK complex constitute various checkpoints to ensure the correct sequence of events and products are formed in each phase of cell division. The checkpoints at each phase has a specific role. They are -

G1 phase: Ensures that the physical space required for the resultant daughter cells, chromosomal DNA produced from the last cycle of division isn't damaged.

S phase: Regulates the DNA replication machinery.

G2 phase: Checks if DNA or chromosomes have been duplicated before the M-phase can begin.

M phase: Attachment of kinetochore in every chromatid to spindle fibers.

Thus, cyclin-CDK complexes act as molecular regulators or molecular switches so that the cell cycle always progresses in one direction with no errors in resultant daughter cells.