Complementary DNA or cDNA is a complementary copy of a stretch of DNA produced by recombinant DNA technology.

CDNA or Complementary DNA
cDNA Library construction

Complementary DNA is a type of DNA that is created by the enzyme reverse transcriptase. Reverse transcriptase is an enzyme that can produce DNA from RNA.

Reverse transcriptase is made up of 2 subunits, and this enzyme is found in certain viruses. For example, the AIDS virus is a retrovirus and has reverse transcriptase, which is what allows it to make a DNA copy of the RNA of HIV virus.

Scientists use complementary DNA as a tool to study genetic disorders because they know what the DNA of healthy cells should look like. They can then use complementary DNA to find out what the DNA of cells without the disorder looks like. Complementary DNA is also used in genetic engineering. The DNA found in living organisms can be changed by the addition of specific genes.

To achieve this, scientists cut a gene from a chromosome and use complementary DNA to replace it. This is known as DNA cloning.

The reparation of cDNAs is often the first step in cloning DNA sequences of interest.

It is used as specific and sensitive probes in hybridization studies because cDNAs usually do not include regulatory or other controlling sequences, and so they can be used to identify (probe) and isolate genes and their associated sequences from genomic DNA.

Complementary DNA (cDNA) clone

A double-stranded DNA molecule that is carried in a vector and was synthesized in vitro from an mRNA sequence by using reverse transcriptase and DNA polymerase.

Complementary DNA (cDNA) cloning

A method of cloning the coding sequence of a gene, starting with its mRNA transcript. It is normally used to clone a DNA copy of a eukaryotic mRNA. The cDNA copy, being a copy of a mature messenger molecule, will not contain any intron sequences and may be readily expressed in any host organism if attached to a suitable promoter sequence within the cloning vector.

Complementary DNA (cDNA) library

A collection of cDNA clones that were generated in vitro from the mRNA sequences isolated from an organism or a specific tissue or cell type or population of an organism.

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