Complementary DNA

In genetics, complementary DNA (cDNA) is DNA synthesized from a mature mRNA template. cDNA is often used to clone eukaryotic genes in prokaryotes.

Synthesis

Though there are several methods for doing so, cDNA is most often synthesized from mature (fully spliced) mRNA using the enzyme reverse transcriptase. This enzyme operates on a single strand of mRNA, generating its complementary DNA based on the pairing of RNA base pairs (A, U, G, C) to their DNA complements (T, A, C, G).

Related Topics:
Reverse transcriptase - Base pair

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To obtain eukaryotic DNA whose introns have been spliced:

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• A eukaryotic cell transcribes the DNA into mRNA.
• The same cell processes the nascent mRNA strand by splicing out introns, and adding a poly-A tail and GTP cap.
• This mature mRNA strand is extracted from the cell.
• A poly-T oligonucleotide is hybridized onto the poly-A tail of the mature mRNA template. (Reverse transcriptase requires this double-stranded segment as a primer to start its operation.)
• Reverse transcriptase is added, along with deoxynucleotide triphosphates (A, T, G, C).

The reverse transcriptase scans the mature mRNA and synthesizes a sequence of DNA that complements the mRNA template. This strand of DNA is complementary DNA.

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