Bacterial artificial chromosome

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A bacterial artificial chromosome (BAC) is a DNA construct, based on a fertility plasmid (or F-plasmid), used for transforming and cloning in bacteria, usually E. coli. F-plasmids play a crucial role because they contain partition genes that promote the even distribution of plasmids after bacterial cell division. The bacterial artificial chromosome's usual insert size is 150 kbp, with a range from 100 to 300 kbp. A similar cloning vector, called a PAC has also been produced from the bacterial P1-plasmid.

BACs are often used to sequence the genetic code of organisms in genome projects, for example the Human Genome Project. A short piece of the organism's DNA is amplified as an insert in BACs, and then sequenced. Finally, the sequenced parts are rearranged in silico, resulting in the genomic sequence of the organism.

They can also be utilised in genetic disease models, often with mice, as in the study of complex genes it can carry both the gene and various promoter sequences which can often show the genes true expression level. BACs have been used to some degree of success with mice when studying neurological diseases such as Alzheimer's and aneuploidy with Down's syndrome. There have also been instances when they have been used to study specific oncogenes associated with cancers. They are transferred over to these genetic disease models by electroporation/transformation, transfection with a suitable virus or microinjection. BACs can also be utilised to detect genes or large sequences of interest and then used to map them onto the human chromosome using BAC arrays.