Cosmid
From Free net encyclopedia
A cosmid is a type of plasmid (often used as a cloning vector) constructed by the insertion of cos sequences, DNA-Sequences of the Phage Lambda Virus.
Cos sequences are single stranded sequneces of DNA, which have been split from the parent molecule by a specific restriction enzyme in such a way that the ends have specific affinity for each other, and hence are known as cohesive ends.
These DNA-Sequences make it possible to pack genes with up to 40K base pairs, while normal plasmids are able to carry only 10-15K base pairs. Cosmids are packeted in phagestructures consisting of proteins, which allows the foreign genes to be inserted into the bacteria. If the Cosmids contain, for example, genes for resistance against antibiotics, the transfected bacteria are then able to survive and to spawn in a nutrient solution containing the antibiotic. Cosmids can be used to build genomic libraries.
References
- Bruce A. Voyles (2002) The biology of viruses 2nd ed. ISBN 0-07-237031-9
- Stryer, Lubert (1995) Biochemistry 4th ed. ISBN 0-7167-2009-4Template:Biotech-stub