Genomic Library—Precise Definition What is a genomic library in the context of molecular cloning and genomics?

Introduction / Context:
A genomic library represents the entire genome of an organism as a set of overlapping cloned fragments. It enables researchers to isolate any gene by screening the library rather than purifying it directly from genomic DNA every time.

Given Data / Assumptions:

• Genomic DNA is fragmented (mechanically or by restriction enzymes).
• Fragments are ligated into vectors (plasmids, phage, BACs).
• The collection is large enough to cover the genome with redundancy.

Concept / Approach:
By distributing genomic fragments across a population of recombinant clones, each clone carries a piece of the genome. Hybridization or PCR screening with gene-specific probes identifies clones containing the target region. Libraries differ from cDNA libraries, which represent expressed mRNAs.

Step-by-Step Solution:

Verification / Alternative check:
Coverage calculations (e.g., using the Clarke–Carbon equation) estimate library size required to capture sequences with a desired probability.

Why Other Options Are Wrong:

• A digital database is an in silico resource, not a physical library of clones.
• A manual is not a library; a single plasmid cannot carry a whole chromosome in one piece for most organisms.

Common Pitfalls:
Confusing genomic libraries with cDNA libraries; the former include introns, promoters, and non-coding regions, the latter represent processed transcripts.

Final Answer:
A collection of many clones, each carrying different DNA fragments from the same organism inserted into vectors