Animal Biotechnology

GENOMIC LIBRARY

• A genomic library contains DNA fragments that represent the entire genome of an organism.
• The first step in creating a genomic library is to break the DNA into manageable size pieces (e.g. 15–20 kb for phage λ vectors), usually by partial restriction endonuclease digest. This generates a continuum of overlapping fragments.
• The next step is to purify fragments of optimal size by gel electrophoresis or centrifugation techniques.
• The final step is to insert the DNA fragments into a suitable vector. Bacteriophage λ or cosmid vectors are typically used for genomic libraries.
• In humans, the genome size is approximately 3 × 10⁹ bp. With an average insert size of 20 kb, the number of random fragments to ensure with high probability (95–99%) that every sequence is represented is approximately 10⁶ clones for humans.