Structural Biochemistry/DNA recombinant techniques/Artificial Chromosomes/Bacterial Artificial Chromosomes (BAC)
Bacterial Artificial Chromosomes (BAC)
Bacterial Artificial Chromosome also known as BAC is a vector used to clone a target DNA piece and planted in bacterial content. Vectors are carriers that are also made of DNA. The vector acts as a parent host, which can acts like a guide to carry out the gene for cloning. Bacterial artificial chromosomes can be as large as insects. In order to amplify a gene, DNA sequence must be extracted from a desired source using restriction enzymes to cleave the vector and the target DNA and attach into a host bacterium. Plasmids of bacteria usually play a vital role in the cloning process since they are also made of DNA and they can be compatible with experimental gene. Vectors also contain the origin of replication where replication begins at the vector site and proceed with the attached sample.
Common Gene Components
- replicates plasmid replication and regulates copy number
parA and parB
- partitions F plasmid DNA into daughter cells during division and ensures stable maintenance of the BAC
A selectable markers
- because some BACs also have lacZ at the cloning site for blue/white selection, this is used to resist antibiotics
T7 and Sp6
- phage promoters for transcription of inserted genes
Contribution to Models of Disease
BACs are being greatly used in modeling genetic diseases in order to study their effects in the experimentation on transgenic mice. Because complex genes often have many regulatory sequences upstream of the encoding sequence, including many promoter sequences that will control a gene's express level, BACs have been found very useful in this area of study. When tested with mice, BAC has been able to help with the study of neurological diseases, such as Alzheimer's disease or Down syndrome. BAC has also been recently used to study specific oncogenes, which are associated with various different cancers. BAC is transferred over to these genetic disease models through the use of electroporation/transformation, which is essentially transfection with a compatible virus or micro injection. BACs have also been used to detect genes or large sequences of interest, and then used to map them onto the human chromosome using BAC arrays. Because this process is able to accommodate much larger sequences without the risk of rearrangement, it is the preferred method of these types of genetic studies and also more stable than other types of cloning vectors.
BACs can also act as clones of large DNA viruses as well as RNA viruses. These clones are known as "infections clones," as transfection of the BAC construct into host cells is enough to initiate the viral infection in the host. The infectious property that the BACs contain has aided in the study of viruses such as herpesviruses, poxviruses, and coronaviruses. Using genetic approaches to mutate and transform the BAC while it resides in bacteria, molecular studies of these viruses can be performed.
http://www.scq.ubc.ca/ THE BIG BAD BAC: BACTERIAL ARTIFICIAL CHROMOSOMES