Question

The attachment site for microtubules that separates chromosomes during cell division:

• A. Kinetochore
• B. Telomere
• C. Chromatin
• D. Centrosome

Hint:

Centromere = The region of D on a chromosome.
Kinetochore = The protein structure that forms ON the centromere to bind microtubules.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question asks to identify the specific protein structure assembled on chromosome centromeres that directly binds spindle microtubules to orchestrate chromosome movement during mitosis and meiosis.

Step 2: Key Formula or Approach:
During cell division, spindle fibers attach to chromosomes to generate mechanical forces necessary for sister chromatid separation. The macromolecular assembly mediating this binding is the kinetochore.

Step 3: Detailed Explation:

• Kinetochore Assembly: The kinetochore is a complex, multiprotein disk-like structure built directly upon centromeric heterochromatin.

• Microtubule Binding: It serves as the physical interface connecting spindle microtubules (kinetochore microtubules) to the chromosome.

• Force Generation: During metaphase and aphase, kinetochores interact with motor proteins (such as dynein and kinesin) to regulate chromosome alignment along the metaphase plate and pull separated chromatids toward opposite spindle poles.

• Distinction from Other Options:

• Telomere: Protects chromosome ends from degradation.

• Chromatin: The complex of genomic D and histone proteins composing chromosomes.

• Centrosome: The main microtubule-organizing center (MTOC) located at the cell poles from which spindle fibers origite, rather than the attachment point on chromosomes.

Step 4: Fil Answer:
The kinetochore is the specialized protein complex that attaches spindle microtubules to chromosomes during cell division.