what is a cDNA library?

Question

is it a physical library or a data base? i have tried researching online but they all confuse me!

Answer 1

cDNA stands for complementary DNA.
Genes in eukaryotes are fragmented: there are DNA regions which code for a protein (exons) that are interrupted by non-coding DNA (introns). When DNA is transcribed to RNA, the primary RNA transcript has all of these sequences. In order to be translated properly into protein, first it undergoes a process termed splicing, during which introns are removed and exons are "glued" together. This way you get a mature mRNA which has the continuous sequence that will be translated.

Prokaryotes don't have the machinery for splicing. So if you want to express eukaryotic genes in prokaryotes or in vitro you need to clone the "mature" sequence. So you use a special enzyme which is called reverse transcriptase which uses the mature mRNA as a template to create a complementary DNA. This way you get a DNA (cDNA) which has the information for the gene in a continuous fashion. If you isolate all the mRNA from a eukaryotic organism you can make the cDNA of all expressed genes of that organism and thus make a library. Usually you clone the cDNA into plasmids so that you can easily amplify, store and handle it.

Of course the exact sequences of the cDNAs are also determined and listed in data bases to help research.

Answer 2

neither and both at the same time. it is frozen in a vial in the freezer. so it is physical and it contains data

you take the mRNA of an organism/tissue. mRNA means only the active genes of an organism/the tissue, not all genetic material the organism has

you build the cDNA (complementary string to the mRNA) and you store it and can use it for analysing the genes that are IN USE in the tissue that your sample comes from.

hope it is clear. the point is that every organism has many many genes, but only some are in use (EXPRESSED) in different tissues and under different circumstances. so the library is used to track down the individual genes that play their individual roles. so for instance you take plant leaf tissue, subject it to hot temperature, so it starts producing so called heat shock protteins. collect the tissue, extract the mRNA - the active genes, make the cDNA and you have most probably the genes for those heat shock proteins in you hand - only you need to compare it to the same experiment without the heat shock.

Answer 3

Concise Oxford English Dictionary

cDNA
■ abbreviation complementary DNA.



© Oxford University Press, 2004



Merriam-Webster Collegiate® Dictionary

cDNA
Pronunciation: 'sē-ˌdē-(ˌ)en-'ā, ˌsē-
Function: noun
Etymology: complementary
Date: 1973

: a DNA that is complementary to a given RNA which serves as a template for synthesis of the DNA in the presence of reverse transcriptase



© 2005 Merriam-Webster, Incorporated

Answer 4

A cDNA libary is a set of cDNA clones (mRNA turned back into DNA and cloned into something eg a plasmid or cosmid). Its phyical DNA sequences in plasmids etc. The sequences might be sequenced and the sequences put into a database though.

Answer 5

It is a term given to a library of DNA on someting so for example humans have many cDNA libraries because we contain lots of DNA. Read more on: http://en.wikipedia.org/wiki/CDNA_library.
Hope it helps,
thesisnaco

Answer 6

cDNA is complementary DNA.
Its infact mRNA that is complemetary to DNA

Answer 7

Both