Advanced Molecular Microbiology Techniques
Complimentary DNA (cDNA) is the DNA synthesised from messenger RNA (mRNA). The reaction is catalysed by two enzymes; reverse transcriptase as well as DNA polymerase. As per the central dogma of life, DNA is transcribed to mRNA, which is subsequently translated to proteins to carryout the cell’s functions. The major difference between the prokaryotic and eukaryotic mRNA is the presence or absence of intron sequences among the exons. During transcription of eukaryotic mRNA, intron sequences are spliced-off, which can further be translated to the amino acids to carry out their desired function. As prokaryotic genes do not contain introns, their RNA is not subjected to cutting and splicing. Thus, complementary DNA is used for gene cloning or as gene probes or in the creation of cDNA libraries. The widest application of cDNA is to monitor the expression level of specific functional genes by using quantitative real-time PCR (qRT-PCR) with cDNA as template.