Bacterial artificial chromosome
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. The bacterial artificial chromosome's usual insert size is 150–350 kbp.[4] A similar cloning vector called a PAC has also been produced from the DNA of P1 bacteriophage.
BACs are often used to
next-gen sequencing
.
Common gene components
- repE
- for plasmid replication and regulation of copy number.
- parA and parB
- for partitioning F plasmid DNA to daughter cells during division and ensures stable maintenance of the BAC.
- A selectable marker
- for blue/white selection.
- T7 & Sp6
- phage promoters for transcription of inserted genes.
Contribution to models of disease
Inherited disease
BACs are now being utilized to a greater extent in
promoter sequences that will govern a gene's expression level. BACs have been used to some degree of success with mice when studying neurological diseases such as Alzheimer's disease or as in the case of aneuploidy associated with Down 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 utilized to detect genes or large sequences of interest and then used to map them onto the human chromosome using BAC arrays. BACs are preferred for these kind of genetic studies because they accommodate much larger sequences without the risk of rearrangement, and are therefore more stable than other types of cloning vectors.[citation needed
]
Infectious disease
The genomes of several large
RNA viruses have been cloned as BACs. These constructs are referred to as "infectious clones", as transfection of the BAC construct into host cells is sufficient to initiate viral infection. The infectious property of these BACs has made the study of many viruses such as the herpesviruses, poxviruses and coronaviruses more accessible.[5][6][7] Molecular studies of these viruses can now be achieved using genetic approaches to mutate the BAC while it resides in bacteria. Such genetic approaches rely on either linear or circular targeting vectors to carry out homologous recombination.[8]
See also
- Cosmid
- End-sequence profiling
- Fosmid
- Human artificial chromosome
- Secondary chromosome
- Yeast artificial chromosome
References
External links
- The Big Bad BAC: Bacterial Artificial Chromosomes — a review from the Science Creative Quarterly
- Empire Genomics (company that sells BAC clones from genomic libraries)
- Amplicon Express (company that makes custom BAC libraries)