DNA cloning is a fundamental technique in recombinant DNA technology. It can be defined as a method of isolation and amplification of precise DNA fragments so that billions identical molecules are pure in a tube and can be used in subsequent experiments. It is not wrong to consider cloning of a gene as its purification. The aim of cloning is to allow the study of the cloned molecule in terms of sequence and function. It is also common to clone a nucleic acid molecule in order to use it as a probe. In other words, cloning is necessary to study all related gene aspects as purification of proteins is necessary to study their functions.
What cloning involves ?
Cloning involves construction of hybrid DNA molecules (recombinant) that are able to self-replicate in a host cell, usually bacteria. This is accomplished by inserting DNA fragments into a plasmid or bacteriophage cloning vector, introducing the vector into bacterial cells where it is amplified by the bacterial replication machinery. The inserted DNA fragment, or insert, may be derived from any organism and obtained from genomic DNA, cDNA, previously cloned DNA, PCR or it can be synthesized in vitro.
Cloning by library construction (cDNA library, genomic library) was always applied before development of PCR technique which enables more rapid DNA cloning.
This subject is continued on this website in the pdf entitled “principles of DNA library – banque d’ADN” under the section “chapitre de cours” or may can click here to download the pdf.
