(i) RNA-dependent DNA polymerase enzyme is used for the synthesis of a complementary DNA strand from RNA molecule as a template. It is produced by HTV and other retroviruses which help them to synthesize DNA from their viral RNA.
(ii) Isoelectric focusing (IEF), also known as electrofocusing, is a technique for separating different molecules by their electric charge differences. It is a type of zone electrophoresis, usually performed on proteins in a gel.
(iii) Cosmids are constructed by uniting some part of the bacterial plasmids with a ‘ori’ gene, an antibiotic selection marker and a cloning site with one or more recently two ‘cos’ sites derived from bacteriophage lambda.
(iv) A vitamin is an organic compound required as a nutrient in very small amounts by an organism. They act as co-factor of an enzyme. It cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet.
