Question

What are DNA libraries, write their types, advantages and disadvantages?

Answer 1

Hint: The genome of an organism consists of several millions and billions of base pairs of DNA, thus they make up thousands of genes collectively. So for research purposes and studying genomic elements in detail, the DNA is broken into smaller and manageable fragments and is kept in the form of well maintained genomic libraries.

Complete answer:
A DNA library also called a gene library is the collection of DNA sequences from different organisms. These DNA sequences are first extracted, then purified and at the last it is sequenced that can be used for the purpose of analysis, comparative detection studies.
DNA libraries are made by cutting the genome of interest with a RE- restriction enzyme to generate large fragments, insertion of these fragments is done into a vector, and then putting each vector into a bacterial cell.

The DNA library is categorized into two types:
Genomic Library: In these types of DNA libraries, the complete genome of an organism is used. The genomic information of the complete genome is made to store. These can be further of two types:
>Nuclear Genomic Library- DNA obtained from the nucleus is purified and stored.
>Organelle Genomic Library- DNA obtained from the cell organelles (like mitochondria or chloroplast) is purified and stored.

cDNA Library: When the mRNAs from a cell are extracted and DNA is synthesized from that mRNA through the process of reverse transcription, such a DNA is called cDNA (complementary DNA). Also, cDNA library has a collection of mRNAs of an organism, in the form of cDNA.

>Advantages of DNA libraries:

-It can be used for the cloning of full-length cDNA molecules.
-For the study of mRNAs expression in different cells or tissues.
-Study of splicing in different cells or tissues.
-Creation of transgenic organisms.
-For the study of genetic defects in the pharmaceutical industry.
-To determine the complete genome sequence of any living organism.
-In genetic engineering, as it has complete genomic sequence for generation of transgenic animals
-Study the function of regulatory sequences in DNA.
-Study of genetic mutations in cancer tissues.

Disadvantages of DNA libraries:
-Extraction of larger DNA and its sequencing is a difficult task.
-cDNA libraries give a picture of exons only, the alternative splicing is not considered.
-Contamination of DNA.

Note: Genomic libraries have facilitated the complete resolution of the DNA sequences of tens of bacterial genomes, entire genome of the yeast, the genomes of a worm also known as Caenorhabditis elegans, genome an insect i.e. Drosophila melanogaster, genome of a plant- Arabidopsis thaliana, and complete human genome.