Question

Describe three major structural changes in chromosomes that can lead to genetic abnormalities.

Answer 1

Chromosomes are carriers of heredity and they contain DNA which is carried over to the next generation. Hence any difference in the number and structure of chromosomes can have dangerous implications on the individual as it can alter the expression of genes, leading to several abnormalities.

Here, lets discuss on the structural changes in a chromosome which can lead to genetic disorders.

1. Deletion - A portion of the chromosome is lost from it, thus causing it to be missing or deleted. In that case, the genes present in the missing region are'not expressed and mutated proteins form which in turn cause lethal consequences. A disorder named as Wolf - Hirschhorn syndrome is caused by partial deletion of chromosome number 4.

2. Duplication - A portion of the chromosome is duplicated or copied into the chromosome, resulting in added genetic material, thus causing over expression of genes and proteins which are harmful to the organism. Charcott - Marie Tooth disease is an abnormality caused by duplication of gene encoding peripheral myelin protein 22 on chromosome 17.

3. Translocation - Translocation is a change in location of a part of chromosome within the chromosome or to a different chromosome. This causes flaws in chromosomes, causing the absence of necessary proteins in an organism. Eg of such a disease caused by translocation is Berkett's Lymphoma which is caused by reciprocal translocation.