Question

The most useful plasmid for cloning is

Answer 1

The process of making multiple copies of a fragment of DNA is called DNA cloning. A plasmid is used as a vector to carry the desired DNA fragment into bacteria which reproduces to produce multiple copies of this DNA which are called clones.

Complete answer:
The plasmid is a small, circular, extrachromosomal DNA molecule. It is single-stranded and has the ability to replicate autonomously and is not under the control of chromosomal DNA. It is found in bacteria and some eukaryotes like yeast.

Because of its ability to replicate, plasmid acts as a cloning vector in recombinant DNA technology for manipulating genes. The most useful plasmid for cloning is pBR322.

Following are the characteristics of pBR322-
- Restriction sites: BamH I, Hind III, Pvu I, Pvu II, Pst I, EcoR I
- Selectable marker: antibiotic resistance genes for ampicillin and tetracycline
- ORI: the origin of replication
- ROP: It codes for proteins involved in the process of replication of plasmid

Hence, we can say that the most useful plasmid for cloning is pBR322.

Additional Information: The technology used to produce artificial DNA by combining various DNA fragments having desired genes is called recombinant DNA technology or genetic engineering. It can be accomplished by using specific tools- restriction enzymes, polymerase enzymes, ligases, cloning vectors and the host organism.

Note: Alternative selectable marker help in differentiating recombinants from non-recombinants by producing coloured colonies when reacted with a chromogenic substrate. A recombinant DNA is inserted within the coding sequence of an enzyme, β-galactosidase. This causes the inactivation of the gene for the synthesis of this enzyme. This is referred to as insertional inactivation.