Question

Assertion: Small disc-shaped structures at the surface of the centromeres are called kinetochores.
Reason: Kinetochores serve as the sites of attachment of spindle fibres to the centromeres.

• A. Both assertion and reason are true and the reason is the correct explanation of the assertion.
• B. Both assertion and reason are false.
• C. Assertion is true but reason is false.
• D. Both assertion and reason are true and the reason is not the correct explanation of the assertion.

Answer 1

The correct option is D Both assertion and reason are true and the reason is not the correct explanation of the assertion.

During metaphase discontinuous fibres radiate out from two spindle poles and get connected to the disc shaped structure at the surface of the centromere called kinetochores. These are called chromosome fibres or spindle fibres. A kinetochore is a complex protein structure; it is the point where microtubules attach themselves to the chromosome.