Question

In onion root tip during mitotic metaphase, the number of kinetochores is
A. 4
B. 64
C. 32
D. 16

Answer 1

Kinetochore is a disc-shaped protein structure found in the eukaryotic cells, these kinetochores are mainly associated with the duplicated chromatids the where the spindle fibers are attached to pull the chromatids during the cell division.

Complete answer:
Kinetochore contains two regions such as inner and outer kinetochores.
An inner kinetochore, usually tightly associated with the centromere DNA.
At the same time, inner kinetochore is combined with a specialized form of chromatin that is present all over the cell cycle.
The outer kinetochore is generally a very dynamic structure, and it also interacts with the microtubules, this outer component has identical structures, which are assembled and functional only during cell division.
Generally, the simplest form chromosome also consists of at least 19 different proteins.
Important functions of the kinetochore.
Kinetochore helps in anchoring of chromosomes to Microtubules in the spindle.
And these kinetochores are also helped in the verification of anchoring,
It helps with the activation of the spindle checkpoint.
Kinetochore usually participates in the production of force to propel chromosome movement during cell division.
Number of Kinetochores in the onion root tip
Onion root means nothing but somatic cells, each somatic cell of an onion contains 8 chromosomes.
During cell division and in the metaphase, chromosomes get doubled, so in the metaphase stage, the root of the onion has 16 cells.
Each cell contains 2 kinetochores.

So 16 multiplied with 2, so the answer is 32.

Note: During cell division, the number of microtubules attached to the Kinetochores is generally varied, whereas, in lower organisms, one microtubule is attached to the kinetochore, but in the case of mammals, each kinetochore may be attached to 15 to 25 microtubules.