Question

Centromere is that part of the chromosome where
A. Nucleoli are formed
B. Crossing over takes place
C. Chromatids are attached
D. Nicking occurs

Answer 1

Hint: In the chromosomes, centromere acts as a binding thread in a chromosome, where the arms of the chromosomes are attached. There are four various shapes according to the position- submetacentric, metacentric, telocentric, and acrocentric chromosomes.

Complete answer: The chromosomes are the thread-like structures that carry genetic information from one generation to another generation.

-The arm of a chromatid has an outer protective covering known as the pellicle. The pellicle is the proteinaceous covering of the chromosome. It is the non-genetic part. Inside the pellicle, the matrix is filled. The arm contains the Chromonemata. This chromonemata is the genetic part and contains the DNA and Histone proteins. There is a primary constriction present in all the chromosomes that are known as the centromere.
-The centromere can be present anywhere on the chromosome. It connects the arms or the chromatids that are formed during the division. The centromere has a plate-like covering on its sides known as the Kinetochore. The tip of the chromosome is called the Telomere. Sometimes, the chromosomes have a secondary constriction also. The part beyond the secondary constriction is the satellite. Such types of chromosomes are known as the SAT.
Thus, Option C, i.e., Centromere is that part of the chromosome where the chromatids are attached.

Note: The difference between the arms and the chromatids is that the arms are before the division. However, during the interphase stage of the cell division, the chromonemata double inside the arms of the chromosomes. These chromosomes then separate during the metaphase and four arms are formed from the two. These arms are then known as the chromatids. But this separation does not occur at the centromere, until the anaphase.