- CDNA library
A
cDNA library is a collection of cloned cDNA (complementary DNA) fragments. cDNA is produced from fully transcribedmRNA 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 aboutenhancers ,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 asreverse transcriptase . In eukaryotic cells, a poly-(A) tail (consisting of a long sequence of adenine nucleotides) distinguishes mRNA fromtRNA andrRNA and can therefore be used as aprimer site for reverse transcription. Several methods exist for purifying RNA such astrizol extraction andcolumn purification . Once mRNA is purified, oligo-dT and random primers can be used with reverse transcriptase to create cDNA templates.Restriction endonucleases andDNA ligase are then used toclone the sequences into bacterialplasmid s.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
Wikimedia Foundation. 2010.