Molecular cloning refers to the process by which recombinant DNA molecules are produced and transformed into a host organism, where they are replicated. A molecular cloning reaction is typically comprised of the following two components: The DNA fragment of interest to be replicated A vector/plasmid backbone that contains all of the components for replication in the host DNA of interest, such as a gene, regulatory element(s), or operon, etc., is prepared for cloning by excising it out of the source DNA using restriction enzymes, copying it using the Polymerase Chain Reaction (PCR), or assembling it from individual oligonucleotides. At the same time, a plasmid vector is prepared in linear form using restriction enzymes or PCR. The plasmid is a small, circular piece of DNA that is replicated within the host, and exists separately from the host’s chromosomal or genomic DNA. By physically joining the DNA of interest to the plasmid vector through phosphodiester bonds, the DNA of interest becomes part of the new recombinant plasmid and is replicated by the host.
