To circumvent this, phage transduction is used instead. Plasmids become unstable after a certain amount of DNA has been inserted into them, because their increased size is more conducive to recombination. However, unlike plasmids, they can also be packaged in phage capsids, which allows the foreign genes to be transferred into or between cells by transduction. Those cells which did not take up the cosmid would be unable to grow. They frequently also contain a gene for selection such as antibiotic resistance, so that the transfected cells can be identified by plating on a medium containing the antibiotic. They can replicate as plasmids if they have a suitable origin of replication: for example SV40 ori in mammalian cells, ColE1 ori for double-stranded DNA replication or f1 ori for single-stranded DNA replication in prokaryotes. Copy control vector can be used for easy DNA purification from fosmid clones.Guide to balance cleaning: 8 simple stepsĬosmids are able to contain 37 to 52 kbp of DNA, while normal plasmids are able to carry only 1-20 kbp.

We also offer customer library screening for positive clones. We offer non-arrayed libraries and arrayed libraries (colony picking, replicate plates, high density filters). Our optimized methods are reliable, fast and cost effective.įigure 2: Size determination of fosmid clones. Obtained inserts sizes are always uniform and range within 35-45Kb (Please see below Figure 2). Proprietary high efficiency cloning methods guarantee high quality and genome coverage that customers need. Guaranteed high quality and genome coverage A physically random sheared fosmid library will dramatically reduce the costs for downstream application(s) such as end-sequencing and screening.įigure 1: Physically sheared HMW DNA (Lane 1: un-sheared, Lanes 2-4: sheared). To achieve true randomness of inserts, our fosmid libraries are generated by random physical shearing of high molecular weight DNA (Please see Figure 1) using proprietary methods. The key step for fosmid library is preparation of inserts suitable for cloning into the fosmid vector. This allows scientiststhe needed flexibility in providing DNA to construct a library. Fosmid libraries, contrary to BAC large-insert libraries, do not require HMW DNA (typically 2Mb) as a starting material.

Although we greatly prefer to perform the DNA isolation at our facilities we understand that this is not always feasible. Also, the copy control vector can be used for easy DNA purification from fosmid clones.įosmid libraries are commonly used for closing gaps in a whole genome sequence, physical maping, metagenomic and expression screening and more. Because of this property, they are present in low copy number and consequently more stable than cosmids. 40kb) to cosmids, but, like BAC clones, they contain replicons derived from the F factor for DNA replication and segregation.

Difference between plasmid and cosmid