Question

Identify the types of chromosomes shown in A, B, C, D based on the position of centromeres.

Answer 1

Hint: Every chromosome essentially has a primary constriction of the centromere on the sides of which disc-shaped structures called kinetochores are present. Based on the position of centromeres chromosomes are classified into 4 types. The names of all these 4 types end with centric.

Complete answer:
Centromere- it is the specialized sequence of DNA of a chromosome that joins the pair of sister chromatids. On the side of each centromere, a disc-shaped structure called kinetochores (during mitosis the spindle fibers attached to the centromere via kinetochores) are present.

In the figure given above, there are four types of chromosomes based on the position of the centromere. These are:
A. Metacentric- The metacentric chromosome has a middle centromere forming two equal arms of the chromosome.
B. Sub metacentric- The submetacentric chromosome has a centromere slightly away from the middle of the chromosome resulting in one shorter arm and one long arm.
C. Acrocentric- In the case of acrocentric chromosomes the centromere is situated close to its end forming one extremely short and one very long arm.
D. Telocentric- The telomeric chromosome has a terminal centromere. The arms are visible barely.
Each chromosome has two arms and these arms are connected in either these four types.

Note: All these four types of chromosomes are differentiated on the basis of the position of the centromere like being in the center or making the short and long arm. These chromosomes also have some shapes like-
- Metacentric, these are V-shape.
- Sub metacentric, these are L shaped.
- Telocentric, these are “I” shaped.