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A transformation efficiency of 1×10 8 cfu/μg for a small plasmid like pUC19 is roughly equivalent to 1 in 2000 molecules of the plasmid used being introduced into cells. In E. coli , the theoretical limit of transformation efficiency for most commonly used plasmids would be over 1×10 11 cfu/μg.
For example, pBR322 is a medium copy number plasmid (~20 copies/cell) from which several high copy number cloning vectors (>100 copies/cell) have been derived by mutagenesis, such as the well known pUC series. [1] This delivers the convenience of high plasmid DNA yields but the additional burden of the high copy number restricts the plasmid size.
A pUC19 cloning vector showing the multiple cloning site sequence with restriction enzyme sites. A multiple cloning site (MCS), also called a polylinker, is a short segment of DNA which contains many (up to ~20) restriction sites—a standard feature of engineered plasmids. [1]
(Typical transgene delivery methods involve plasmids, which contain foreign DNA.) The smaller size of minicircles also extends their cloning capacity and facilitates their delivery into cells. Their preparation usually follows a two-step procedure: [4] [5] production of a 'parental plasmid' (bacterial plasmid with eukaryotic inserts) in E. coli
They are the standard cloning vectors and the ones most commonly used. Most general plasmids may be used to clone DNA inserts of up to 15 kb in size. One of the earliest commonly used cloning vectors is the pBR322 plasmid. Other cloning vectors include the pUC series of plasmids, and a large number of different cloning plasmid vectors are ...
Cells which have been successfully transformed with pUC19 can be differentiated from cells which have not by growing them on media with ampicillin. Only the cells with the plasmid containing amp R will survive. The origin of replication (ori), is derived from the plasmid pMB1. [6] [1] pUC19 is a high copy number plasmid. [3]
Plasmid sizes vary from 1 to over 1,000 kbp. I doubt that there are any plasmids smaller than roughly 500 bp. Plasmids vary in size; the smallest plasmid is only 846 bp long and contains only one gene. [1] Markus29 13:37, 6 February 2013 (UTC)
The circular sequence is numbered such that 0 is the middle of the unique EcoRI site and the count increases through the Tet R gene. If we have to remove ampicillin for instance, we must use restriction endonuclease or molecular scissors against PstI and then pBR322 will become anti-resistant to ampicillin.