Question

In how many groups are the 23 human chromosome pairs divided?
A. Nine
B. Seven
C. Five
D. Eleven

Answer 1

Hint: Chromosomes are the thread-like structures that carry genetic information from one generation to another generation. Humans have 23 pairs of chromosomes out of which 22 pairs are the genetic chromosomes known as the autosomes and one pair is the sex chromosomes known as the allosomes.

Complete answer:
Karyotyping refers to the arrangement of the chromosomes on the basis of their size, the position of the centromere, the ratio of arms, and orientation during the anaphasic movement. Humans have an asymmetric type of karyotyping. As per the rules of karyotyping, the twenty-two autosomes are arranged on the basis of their size first and then the two sex chromosomes, X and Y are arranged at the end. The twenty-three human chromosome pairs are divided into seven groups from A to G. This division is done on the basis of the length of the chromosomes and the centromere positions. Thus, based on the above information we can conclude that the 23 human chromosome pairs are divided into seven groups.
Hence, the correct answer is option (B).

Note:
Karyotyping of chromosomes is of two types. These two types are as follows –
1. Symmetric Karyotyping – Symmetric karyotyping is a primitive type of karyotyping. In this type of karyotyping, there is a minimum difference between the largest chromosome and the smallest chromosome. Most of the chromosomes in a symmetric karyotyping are of a metacentric type. This means that the centromere lies exactly at the center of the arms of the chromosomes. Due to this reason, both the arms are equal in size.
2. Asymmetric karyotyping – Asymmetric karyotyping is an advanced type of karyotyping. In this type of karyotyping, there is a huge difference between the largest chromosome and the smallest chromosome. The position of the centromere on the chromosome is variable.