Editing Bacterial artificial chromosome

{{Short description|DNA construct}}
A '''bacterial artificial chromosome''' ('''BAC''') is a [[DNA construct]], based on a functional fertility [[plasmid]] (or [[F-plasmid]]), used for [[Transformation (genetics)|transforming]] and [[cloning]] in [[bacteria]], usually ''[[Escherichia coli|E. coli]]''.<ref name="OConnor1989">{{cite journal | vauthors = O'Connor M, [[Mark Peifer|Peifer M]], Bender W | title = Construction of large DNA segments in Escherichia coli | journal = Science | volume = 244 | issue = 4910 | pages = 1307–12 | date = June 1989 | pmid = 2660262 | doi = 10.1126/science.2660262 | bibcode = 1989Sci...244.1307O }}</ref><ref name="Shizuya1992">{{cite journal | vauthors = Shizuya H, Birren B, Kim UJ, Mancino V, Slepak T, Tachiiri Y, Simon M | title = Cloning and stable maintenance of 300-kilobase-pair fragments of human DNA in Escherichia coli using an F-factor-based vector | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 89 | issue = 18 | pages = 8794–7 | date = September 1992 | pmid = 1528894 | pmc = 50007 | doi = 10.1073/pnas.89.18.8794 | bibcode = 1992PNAS...89.8794S | doi-access = free }}</ref><ref>{{cite journal | vauthors = Shizuya H, Kouros-Mehr H | title = The development and applications of the bacterial artificial chromosome cloning system | journal = The Keio Journal of Medicine | volume = 50 | issue = 1 | pages = 26–30 | date = March 2001 | pmid = 11296661 | doi = 10.2302/kjm.50.26 | url = http://www.kjm.keio.ac.jp/past/50/1/26.pdf | doi-access = free }}</ref>  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 [[base pair|kbp]].<ref name="Stone1996">{{cite journal | vauthors = Stone NE, Fan JB, Willour V, Pennacchio LA, Warrington JA, Hu A, de la Chapelle A, Lehesjoki AE, Cox DR, Myers RM | title = Construction of a 750-kb bacterial clone contig and restriction map in the region of human chromosome 21 containing the progressive myoclonus epilepsy gene | journal = Genome Research | volume = 6 | issue = 3 | pages = 218–25 | date = March 1996 | pmid = 8963899 | doi = 10.1101/gr.6.3.218 | doi-access = free }}</ref> A similar [[cloning vector]] called a [[p1-derived artificial chromosome|PAC]] has also been produced from the DNA of P1 bacteriophage.

BACs were often used to [[sequencing|sequence]] the genomes of organisms in [[genome project]]s, for example the [[Human Genome Project]], though they have been replaced by more modern technologies. In BAC sequencing, 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. BACs were replaced with faster and less laborious sequencing methods like whole genome [[shotgun sequencing]] and now more recently [[Next-generation sequencing|next-gen sequencing]].

==Common gene components==
;''repE'': for plasmid replication and regulation of copy number.
;''[[parABS system|parA]] and [[parABS system|parB]]'': for partitioning F plasmid DNA to daughter cells during division and ensures stable maintenance of the BAC.
;A [[selectable marker]]: for [[antibiotic resistance]]; some BACs also have [[lacZ]] at the cloning site for [[Blue white screen|blue/white selection]].
;''T7 & Sp6'': [[Promoter (genetics)|phage promoters]] for transcription of inserted genes.

==Disease modeling==

===Inherited===
BACs are now being utilized to a greater extent in modeling genetic disease, often alongside [[transgenic]] mice. BACs have been useful in this field as complex genes may have several regulatory sequences upstream of the encoding sequence, including various [[promoter (biology)|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 [[oncogene]]s 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 [[DNA microarray|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|date=January 2011}}

===Infectious===
The genomes of several large [[DNA viruses]] and [[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 [[Herpesviridae|herpesviruses]], [[Poxviridae|poxviruses]] and [[Coronaviridae|coronaviruses]] more accessible.<ref name="Almazan2000">{{cite journal | vauthors = Almazán F, González JM, Pénzes Z, Izeta A, Calvo E, Plana-Durán J, Enjuanes L | title = Engineering the largest RNA virus genome as an infectious bacterial artificial chromosome | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 97 | issue = 10 | pages = 5516–21 | date = May 2000 | pmid = 10805807 | pmc = 25860 | doi = 10.1073/pnas.97.10.5516 | doi-access = free }}</ref><ref name="Domi2002">{{cite journal | vauthors = Domi A, Moss B | title = Cloning the vaccinia virus genome as a bacterial artificial chromosome in Escherichia coli and recovery of infectious virus in mammalian cells | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 99 | issue = 19 | pages = 12415–20 | date = September 2002 | pmid = 12196634 | pmc = 129459 | doi = 10.1073/pnas.192420599 | bibcode = 2002PNAS...9912415D | doi-access = free }}</ref><ref name="Messerle1997">{{cite journal | vauthors = Messerle M, Crnkovic I, Hammerschmidt W, Ziegler H, Koszinowski UH | title = Cloning and mutagenesis of a herpesvirus genome as an infectious bacterial artificial chromosome | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 94 | issue = 26 | pages = 14759–63 | date = December 1997 | pmid = 9405686 | pmc = 25110 | doi = 10.1073/pnas.94.26.14759 | bibcode = 1997PNAS...9414759M | doi-access = free }}</ref> 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]].<ref name="FeederleBartlett2010">{{cite journal | vauthors = Feederle R, Bartlett EJ, Delecluse HJ | title = Epstein-Barr virus genetics: talking about the BAC generation | journal = Herpesviridae | volume = 1 | issue = 1 | pages = 6 | date = December 2010 | pmid = 21429237 | pmc = 3063228 | doi = 10.1186/2042-4280-1-6 | doi-access = free }}</ref>

== See also ==
* [[Cosmid]]
* [[End-sequence profiling]]
* [[Fosmid]]
* [[Human artificial chromosome]]
* [[Secondary chromosome]]
* [[Yeast artificial chromosome]]

== References ==
{{Reflist|30em}}

== External links ==
* [http://www.scq.ubc.ca/?p=266 The Big Bad BAC: Bacterial Artificial Chromosomes] — a review from the [[Science Creative Quarterly]]
* [http://www.empiregenomics.com/products-and-services/bac-clones-and-fish-probes Empire Genomics] (company that sells BAC clones from genomic libraries)
* [https://web.archive.org/web/20110817032210/http://genomex.com/page.php?page= Amplicon Express] (company that makes custom BAC libraries)

{{Nucleic acids}}

{{DEFAULTSORT:Bacterial Artificial Chromosome}}
[[Category:Genomics techniques]]
[[Category:Molecular biology techniques]]