Bacteriophage Lambda Vectors
Yeast Artificial Chromosomes (YACs)
Bacterial Artificial Chromosomes (BACs)
Library Screening and Gene Sequencing
Cosmids are plasmid vectors that contain cos sites. The cos site is the only requirement for
DNA to be packaged into a phage particle. Cosmids were developed in light of this observation.
How do you clone into cosmid vectors?
Since phage particles can accept between 38 and 53 kb of DNA and since most cosmids are about
5 kb, between 33 and 48 kb of DNA can cloned in these vectors.
- Clone the DNA into the vector as you would with any plasmid.
- Introduce the DNA into the bacterial cell via a phage particle.
- Propagate as plasmid.
Problems associated with lambda and cosmid cloning.
Copyright © 1998. Phillip McClean
- Since repeats occur in eukaryotic DNA rearrangements can occur via recombination of the
repeats present on the DNA inserted into lambda or cosmid.
- Cosmids are difficult to maintain in a bacterial cell because they are somewhat unstable.