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Genomic library

 
(′jēn ′lī·brēr·ē)

(genetics) A random collection of cloned deoxyribonucleic acid fragments in a vector; includes all the genetic information of the species. Also known as gene bank.


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Biology Q&A:

What is a gene library?

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A gene library is a collection of cloned DNA, usually from a specific organism. Just as a conventional library stores information in books and computer files, a gene library stores genetic information either for an entire genome, a single chromosome, or specific genes in a cell. For example, one can find the gene library of a specific disease such as cystic fibrosis, the chromosome where most cystic fibrosis mutations occur, or the entire genome of those individuals affected by the disease.

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a set of clones containing DNA fragments that in toto embrace an entire genome. It is prepared by firstly randomly cutting the genomic DNA to give fragments of varying length. The average fragment length is controllable by discrimination in the choice of restriction enzymes used for cutting, and is selected to optimize the length such that fragments will contain entire open reading frames without excessive lengths of additional DNA at either end. Secondly the DNA fragments thus obtained are ligated into a suitable vector (def. 3), which is cloned in a host of choice.

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Wikipedia on Answers.com:

Genomic library

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A genomic library is a population of host bacteria, each of which carries a DNA molecule that was inserted into a cloning vector, such that the collection of cloned DNA molecules represents the entire genome of the source organism. This term also represents the collection of all of the vector molecules, each carrying a piece of the chromosomal DNA of the organism, prior to the insertion of these molecules into the host cells.

Types of vectors

  1. Plasmids: Have a capacity of 15 kb.
  2. Phage (lambda)s: Have a capacity of 25 kb.
  3. Cosmids or Fosmids: Have a capacity of 35-45 kb.
  4. Bacterial artificial chromosomes (BAC)(P-1 derived): Have a capacity of 50-300 kb.
  5. Yeast artificial chromosomes (YAC): Have a capacity of 300- >1500 kb.
  6. Human artificial chromosomes (HAC): Have a capacity of >2000 kb.

Creating a library

The DNA molecules of an organism of interest are isolated. The DNA molecules are then partially digested by an endonuclease restriction enzyme. Sometimes, the DNA molecules are digested for different lengths of time in order to ensure that all the DNA has been digested to manageable sizes. The digested DNA molecules are separated by size using agarose electrophoresis, and a suitable range of lengths of DNA pieces are isolated and ligated into vectors. The vectors can then be taken up by suitable hosts.The hosts are kept in liquid media and can be frozen at -80°C for a long period of time. Usually the hosts are bacteria that do not contain any plasmids, so as to be sensitive to antibiotics.

The process of subdividing genomic DNA into clonable elements and inserting them into hosts is called creating a library, a clone bank or a gene bank. A complete library of host cells will contain all of the genomic DNA of the source organism.


 
 

 

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Wikipedia on Answers.com. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article Genomic library Read more

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