Question

as explained in text book "one antibiotic resistance gene helps in selecting d transformants ,whereas other antibiotic resistance gene helps in slection of recombinants" explain me hw is dis ?what are transformants?

Answer 1

A vector DNA say plasmid usually possesses two antibiotic resistance genes. During the construction of recombinant DNA molecule by genetic engineering, the foreign gene or DNA fragment is inserted at the site of one of the antibiotic resistance gene. Thus, one antibiotic resistant gene remains intact while the other one get inactivated or removed when a foreign gene or DNA fragment is inserted into the vector to produce recombinant DNA. Also, there will be vectors in which desired gene or DNA fragment does not get inserted (non-recombinant vector). When such vectors are allowed to be taken up by host cells during the transformation experiment, some cells will take up the recombinant vector while some will take up non-recombinant vector and some cells will be without any vector. The cells that take up DNA (either recombinant or non recombinant) are known as transformants. While as those which do not are known as non transformants. The cells that take only recombinant DNA are known as recombinants.
These transformants are selected on the basis of intact antibiotic resistance gene while transformants having recombinant vector are selected on the basis of inactivation of resistance gene.