question_answer

(i) What is the significance of mutation?

(ii) Certain mutations are called silent mutation. How?

OR

What are linked genes? How can a pair of linked genes be identified?

 

Answer:

(i)  The sudden appearance or variations are called mutations. They lead to the new phenotypes. Though mutations are random and occur at very slow rates, they are sufficient to create considerable genetic variations for speciation to occur.

(ii) Silent mutation are those which:

(i) Occur at 3rd base position of codon.

(ii) Do not alter expression of the genes.

OR

The genes present in the same chromosome and staying together during inheritance through generations without any change are called linked genes. While unlinked genes are found on different chromosomes.

A pair of linked genes can be easily known from dihybrid cross experiments. The two linked genes do not show independent assortment. They give dihybrid ratio of 3 : 1 instead of 9 : 3 : 3 : 1 and a test-cross ratio 1 : 1 instead of dihybrid test ratio 1:1:1:1.