Complementary DNA (cDNA) is a double-stranded DNA version of an mRNA molecule. In higher eukaryotes, an mRNA is a more useful predictor of a polypeptide sequence than is a genomic sequence, because the introns have been spliced out. Researchers prefer to use cDNA rather than mRNA itself because RNAs are inherently less stable than DNA and techniques for routinely amplifying and purifying individual RNA molecules do not exist. The cDNA is made from mRNA with the use of a special enzyme called reverse transcriptase, originally isolated from retroviruses. Using an mRNA molecule as a template, reverse transcriptase synthesizes a single-stranded DNA molecule that can then be used as a template for double-stranded DNA synthesis. cDNA does not need to be cut in order to be cloned.
Main Difference – DNA vs cDNA
DNA and cDNA are two types of nucleic acids. DNA is the genetic material of most organisms. It is arranged inside the nucleus in eukaryotes. In prokaryotes, DNA is present in the cytoplasm. During the transcription, messenger RNA is produced from the DNA sequences. This mRNA is reverse transcribed by the reverse transcriptase enzyme into complementary DNA or cDNA. The main difference between DNA and cDNA is that DNA is composed of both coding and non-coding sequences whereas cDNA only contains the coding sequences. The coding sequences are the exons of a gene, which codes for a functional protein. The non-coding sequences are the remaining DNA sequences of the genome. Some of the non-coding sequences code for the non-coding RNA such as transfer RNA and ribosomal RNA. Some of the non-coding sequences comprise regulatory elements, which are involved in the regulation of gene expression.