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 referred to as a disc-shaped protein structure that is present in the eukaryotic cells, these kinetochores are mainly connected with the duplicated chromatids the where the spindle fibres are attached to pull the chromatids during the cell division.

Complete answer:
Kinetochore is composed of two regions named as inner and outer kinetochores. An inner kinetochore, usually tightly connected with the centromere DNA.
At the same time, inner kinetochore is attached with a specialized form of chromatin that is located all over the cell cycle.

The outer kinetochore is generally a very dynamic structure, and it also communicates with the microtubules, this outer component has the same structures, which are assembled and performed only during cell division. Generally, the simplest form chromosome is also made up of at least 19 different proteins.

Important functions of the kinetochore include:
Kinetochore plays a major role in anchoring chromosomes to Microtubules in the spindle. And these kinetochores are also needed in the verification of anchoring, It also play role with the activation of the spindle checkpoint.
Kinetochore usually plays a major role in the production of force to propel chromosome movement during cell division.

Number of Kinetochores in the onion root tip can be observed as:
Onion root means nothing but it is referred to as somatic cells, each somatic cell of an onion contains 8 chromosomes. At the time of cell division and in the metaphase, chromosomes get doubled, so in the metaphase stage, the root of the onion possesses 16 cells. Each cell shows presence of 2 kinetochores.
So we multiply 16 with 2, so the answer is 32.

Hence, the correct answer is option (C)

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