Introduction

Plasmids

Bacteriophage Lambda Vectors

Cosmids

Yeast Artificial Chromosomes (YACs)

Bacterial Artificial Chromosomes (BACs)

Library Screening and Gene Sequencing

Course Topics

Course Home
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Cosmids

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?

1. Clone the DNA into the vector as you would with any plasmid.
2. Introduce the DNA into the bacterial cell via a phage particle.
3. Propagate as plasmid.

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.

Problems associated with lambda and cosmid cloning.

1. Since repeats occur in eukaryotic DNA rearrangements can occur via recombination of the repeats present on the DNA inserted into lambda or cosmid.
2. Cosmids are difficult to maintain in a bacterial cell because they are somewhat unstable.

Copyright © 1998. Phillip McClean