A form of DNA prepared in the laboratory using messenger RNA (mRNA) as template, i.e. the reverse of the usual process of transcription in cells; the synthesis is catalysed by reverse transcriptase. cDNA thus has a base sequence that is complementary to that of the mRNA template; unlike genomic DNA, it contains no noncoding sequences (introns), and it is the form of DNA that is sequenced in the RNA-seq technique. cDNA is used in gene cloning for the expression of eukaryote genes in prokaryote host cells, or as a DNA probe to locate particular base sequences in genomic DNA. cDNA molecules are inserted into plasmid or phage vectors to create cDNA libraries of expressed genes.