Question

How can you differentiate genomic libraries and cDNA libraries?

Answer 1

Hint: The genomic revolution that is now taking place relies heavily on genetic libraries. Simply said, a library is a collection of DNA molecules that contain all of the sequence information required for DNA replication in a biological host. Molecules with inserts reflecting a complicated genome or a complex mRNA population from a cell or tissue are also in the collection.

Complete solution:
Genetic libraries are basically divided into two categories – the genomic libraries and the c-DNA (or complementary DNA) libraries. The basic points of differences between the two of them are tabulated below:

Points	Genomic library	c-DNA library
Definition	A genomic library is a collection of DNA fragments which represent the entire genome of the organism.	A c-DNA library is however a collection of c-DNAs which are prepared by extracting m-RNA from the organism’s cell and then subjecting them to Reverse transcriptase PCR (RT-PCR) to yield c-DNA which are cloned into suitable vectors.
Presence of non-coding regions called Introns	Since, a genomic library is a collection of entire genomes it contains both the non-coding regions (introns) and coding regions (exons).	A c-DNA library is prepared from m-RNA therefore it lacks introns and regulatory genes. Therefore, a c-DNA library only contains coding regions.
Size	A genomic library is large in size as it represents entire genomes.	A c-DNA library is short in size as it only contains coding regions of important genes.
Expression in Prokaryotic systems	A genomic library is very difficult to be expressed in prokaryotic systems as they lack intron splicing systems	On the contrary a c-DNA library can be expressed directly into a prokaryotic system as it only contains coding regions of a gene.
Vectors used to make genetic library	A genomic library can be prepared through plasmid, cosmid, lambda phage, BAC, YAC.	c-DNA libraries use phasmids, plasmids, lambda phages etc.

Note:
For sequencing purposes, genomic libraries are widely utilised. They were important in the sequencing of the whole genomes of numerous animals, including the human genome and numerous model species. Different gene libraries provide important genes for cloning experiments in genetic engineering to develop newer ways of enhancing yield and expression like increasing the crop yield.