Question

explain :easy isolation of recombinants from the non-recombinants.

Answer 1

Recombinants can be isolated from non-recombinants by the use of selectable markers:-

1. - Antibiotic resistance gene- It includes ampicillin resistance gene (amp^R) or tetracycline resistance gene (tet^R ), kanamycin resistant gene etc. Suppose amp^R is made inactivated by the insertion of foreign DNA at its place and now the recombinants and non-recombinants are allowed to grow on media containing ampicillin. Those recombinants whose ampR is inactivated will die and do not grow whereas non-recombinants will grow on this media and develop colonies.
2. - Color substance developing gene: -They are known as chromogenic substrates. There is a gene which encodes for â-galactosidase enzyme which develops blue color when grown on chromogenic substrates. This gene is made inactivated by insertion of foreign gene and then the recombinants are allowed to grow on chromogenic substrates. Recombinants will develop colorless colonies and non-recombinants will develop blue color colonies.