Cloning genes

The source of DNA for cloning new genes can be chromosomal DNA (deoxyribonucleic acid) or a DNA copy (cDNA) of a messenger RNA (mRNA).

The choice of molecule (DNA or cDNA) depends on the particular trait required and the methodology.  A collection of DNA or cDNA fragments are produced that can be inserted into appropriate vectors (plasmid or phage) that in turn can be introduced into bacteria for further manipulation and selection.

Electron micrograph of plasmid	Electron micrograph of bacterial phage from the host E. coli