Question

What are the plasmid and where are they found?

Answer 1

A plasmid is an extrachromosomal, self-replicating and double-stranded closed circular DNA molecule.

Plasmids are found in bacteria and lie free in the cytoplasm and may be one to many in number.

Plasmids possess only a few genes which generally give extra survival advantage and some provide resistance to antibiotics.

On the basis of functions, plasmids are of three types:

(a) Fertility (F) factor which promotes sexual conjugation in bacteria.

(b) Resistance (R) factor offer resistance to bacteria against certain drugs.

(c) Colicinogenic (col) factor provides the colicins secreting capacity to bacteria.