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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.
A plasmid is a small, extrachromosomal DNA molecule within a cell that is physically separated from chromosomal DNA and can replicate independently. They are most commonly found as small circular, double-stranded DNA molecules in bacteria ; however, plasmids are sometimes present in archaea and eukaryotic organisms .
(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
Minipreparation of plasmid DNA is a rapid, small-scale isolation of plasmid DNA from bacteria. [20] [21] Commonly used miniprep methods include alkaline lysis and spin-column based kits. [3] [22] It is based on the alkaline lysis method. The extracted plasmid DNA resulting from performing a miniprep is itself often called a "miniprep".
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)
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 bacterial artificial chromosome (BAC) is a DNA construct, based on a functional fertility plasmid (or F-plasmid), used for transforming and cloning in bacteria, usually E. coli. [1] [2] [3] F-plasmids play a crucial role because they contain partition genes that promote the even distribution of plasmids after bacterial cell division.
pBR322 is a plasmid and was one of the first widely used E. coli cloning vectors. Created in 1977 in the laboratory of Herbert Boyer at the University of California, San Francisco, it was named after Francisco Bolivar Zapata, the postdoctoral researcher and Raymond L. Rodriguez. The p stands for "plasmid," and BR for "Bolivar" and "Rodriguez."