Question

Kinetochore is
A. Granule within centromere
B. Surface of centromere
C. Constriction near chromosome end
D. End of chromosome

Answer 1

Kinetochore is a complex disc-shaped protein assembled on the centromeric region of chromosomes where the spindle fibres are attached to pull the chromosomes apart during cell division.

Complete Answer:
Centromere is a distinguished DNA sequence, which joins the two sister chromatids in a chromosome. Kinetochore assembles at the surface of the centromeres that links the spindle microtubules with chromosomes and aids in the cell division.

- Centromere regulates the movement of the chromosomes during mitosis or meiosis. It is also called the primary constriction.
- There are more than 19 proteins in the simplest kinetochore that includes the histone protein that is responsible for the attachment of kinetochores with DNA.
- The unattached kinetochores engage the Mad2 checkpoint protein that helps to seize the mitotic progression unless all the kinetochores are properly attached to microtubules, thereby monitoring the loss of chromosomes.
- In human beings,there are 46 chromosomes. Each chromosome has 2 kinetochores. Hence during mitosis, there are 92 kinetochores.

Therefore the correct answer is (b) Surface of the centromere.

Note: During prometaphase, the kinetochores are assembled at the surface of the centromere and then the spindle microtubules are attached to chromosomes. The proteins present in kinetochore also help in holding the sister chromatids together.