Genomic DNA and c-DNA Distinguish

Properties	c-DNA	Genomic DNA
(i) Principle	A fragment is a clone DNA of an active m-RNA generated by enzyme reverse transcriptase.	The fragment of desired gene is directly obtain from the restriction digestion of genomic DNA.
(ii) Use of primer	When eukaryotic m-RNA is used as template the poly T oligonucleotide is conveniently used as primer.	Either no primer is used or site specific primer is used.
(iii) Utility in case of prokaryotic DNA	The c-DNA is absolutely essential when the expression of an eukaryotic gene is required in a prokaryot.	The prokaryotic genomes do not contain any inhtron. So, their genomic library is directly expressed in the expression vector in appropriate prokaqryotic host.
(iv) Purity of product	The m-RNA is never pure and the mixture of m-RNA is used in c-DNA preparation.	DNA is always pure.
(v) Probe used for identification	The desired gene clone is identified by the probe made up of RNA or c-DNA of m-RNA.	The desired gene clone is identified by the probe made up of DNA.
(vi) Alkaline hydrolysis (vii) RNase	It is necessary in this technique. Used	It is not necessary in this technique. Not used
(ix) Restriction endonuclease	Not used	Used.
(x) Problem	c-DNA library has a problem that m-RNA is always incompletely copied.	Genomic library is under or over represent or even missing of DNA fragments.