Question

What is centromere? How does the position of centrome form the basis of classification of chromosomes. Support your answer by showing the position of centromere on different types of chromosomes.

Answer 1

The region on the chromosome where the spindle fibers bind during the process of cell cycle is called a centromere.
Depending on the position of centromere, chromosomes can be classified into four types:

1. Metacentric chromosome or median centromere: The centromere is present at the centre and thus divides the chromosome into two equal arms.
2. Sub-metacentric chromosome or submedian centromere: The centromere is present slightly away from the centre of a chromosome or nearer to one end of the chromosome. As a result, chromosome is divided into one shorter and one longer arm.
3. Acrocentric chromosome or subterminal chromosome: The centromere is present very cose to one end of the chromosome. Thus, it forms one extremely short and one very long arm.
4. Telocentric chromosome or terminal chromosome: The centromere is present at the terminal end of the chromosome and thus, chromosome appears to have a single arm.