What is the term used to describe the autonomously replicating circul…

The correct answer is Option (3) → Plasmid

Besides their main chromosome, many bacteria carry small rings of DNA that copy themselves on their own. These are plasmids: autonomously replicating, circular, extra-chromosomal DNA. Cohen and Boyer made the first recombinant DNA in 1972 by linking an antibiotic resistance gene with a native plasmid of Salmonella typhimurium.

Option (1) Origin of replication — Incorrect. The origin of replication (ori) is a specific DNA sequence where replication starts. It is a part of a plasmid or chromosome, not the whole circular molecule.

Option (2) Cloning — Incorrect. Cloning is the process of making many identical copies of a piece of DNA in a host. It is a process, not a kind of DNA molecule.

Option (3) Plasmid — Correct. A plasmid is the circular DNA that lies outside the chromosome and replicates independently of chromosomal DNA. Plasmids are widely used as cloning vectors.

Option (4) Recombinant DNA — Incorrect. Recombinant DNA is DNA made by joining pieces of DNA from different sources, for example a foreign gene inserted into a plasmid.

NCERT Extract:
Principles of Biotechnology – “… The construction of the first recombinant DNA emerged from the possibility of linking a gene encoding antibiotic resistance with a native plasmid (autonomously replicating circular extra-chromosomal DNA) of Salmonella typhimurium. Stanley Cohen and Herbert Boyer accomplished this in 1972 by isolating the antibiotic resistance gene by cutting out a piece of DNA from a plasmid which was responsible for conferring antibiotic resistance.”