CDNA library

CDNA library

A cDNA library is a collection of cloned cDNA (complementary DNA) fragments. cDNA is produced from fully transcribed mRNA found in the nucleus and therefore contains only the coding regions of an organism. While information in cDNA libraries is a powerful and useful tool since gene products are readily identified, the libraries lack information about enhancers, introns, and other regulatory elements found in a genomic DNA library.

cDNA Library Construction

cDNA is created from mRNA with the use of an enzyme known as reverse transcriptase. In eukaryotic cells, a poly-(A) tail (consisting of a long sequence of adenine nucleotides) distinguishes mRNA from tRNA and rRNA and can therefore be used as a primer site for reverse transcription. Several methods exist for purifying RNA such as trizol extraction and column purification. Once mRNA is purified, oligo-dT and random primers can be used with reverse transcriptase to create cDNA templates. Restriction endonucleases and DNA ligase are then used to clone the sequences into bacterial plasmids.

The cloned bacteria are then selected , commonly through the use of antibiotic selection. Once selected, stocks of the bacteria are created which can later be grown and sequenced to compile the cDNA library.

cDNA Library uses

cDNA libraries are commonly used when reproducing eukaryotic genomes, as the amount of information is reduced to remove the large numbers of non-coding regions from the library. cDNA libraries are most useful in reverse genetics where the additional genomic information is of less use.

cDNA Library vs. Genomic DNA Library

As previously mentioned, a cDNA library lacks the non-coding and regulatory elements found in genomic DNA. Genomic DNA libraries provide much more detailed information about the organism, but are much more resource-intensive to generate and maintain.

External links

* [http://www.biotecnika.googlepages.com/cdnalibrary.html cDNA library-Properties]
* [http://fantom.gsc.riken.jp/ Functional Annotation of the Mouse database]
* [http://dwb.unl.edu/Teacher/NSF/C08/C08Links/www.dur.ac.uk/~dbl0www/Staff/Croy/cDNAfigs.htm examples of cDNA synthesis and cloning]

References


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