Full Form of BAC

What is Bacterial Artificial Chromosome (BAC)?

A Bacterial Artificial Chromosome (BAC) is a genetic tool used to clone and maintain large DNA fragments in bacteria, typically Escherichia coli (E. coli). It is derived from the F-plasmid, a naturally occurring circular DNA in bacteria, modified to carry foreign DNA inserts ranging from 100 to 300 kilobases (kb). BACs are widely used in genomic research, gene mapping, and sequencing projects, including the Human Genome Project, as they allow stable propagation of large genetic sequences.

BACs function by replicating within bacterial cells, ensuring accurate maintenance and inheritance of the inserted DNA. Researchers use BACs for studying gene function, transgenic models, and disease research. Due to their low mutation rate and high stability, they are ideal for handling large or complex DNA fragments, making them essential in genomic libraries and biotechnology applications.

Formation of Bacterial Artificial Chromosomes (BACs)

The creation of Bacterial Artificial Chromosomes (BACs) involves several steps to efficiently clone and maintain large DNA fragments within bacterial cells, typically Escherichia coli (E. coli).

1. Vector Preparation:
   
   

• A modified F-plasmid from bacteria is used as the BAC vector.

• It contains essential elements like a replication origin, a selectable marker gene (e.g., antibiotic resistance), and cloning sites for inserting foreign DNA.

2. DNA Fragment Isolation:
   
   

• Large DNA fragments (100–300 kb) are extracted from the target organism.

• The DNA is cut into specific fragments using restriction enzymes or mechanical shearing.

3. Ligation into BAC Vector:
   
   

• The isolated DNA fragments are inserted into the BAC vector using DNA ligase, which joins the foreign DNA with the plasmid backbone.

4. Transformation into Bacteria:
   
   

• The recombinant BAC is introduced into E. coli cells through electroporation, allowing bacteria to take up the BAC and replicate it.

5. Selection and Screening:
   
   

• Transformed bacterial cells are grown on antibiotic-containing media to select only those containing the BAC.

• Colonies are screened using PCR or hybridization techniques to confirm the presence of the desired DNA fragment.

6. Replication and Storage:
   
   

• The selected bacterial colonies with BACs are maintained in culture and stored for genomic research, sequencing, or transgenic studies.

Advantages of BACs Over Viral and Nonviral cDNA Vectors

Bacterial Artificial Chromosomes (BACs) offer significant advantages over viral and nonviral cDNA vectors for gene expression studies. Unlike viral vectors, BACs can carry large DNA fragments, including entire genes with their natural chromosomal regulatory elements, ensuring physiologically relevant gene expression. They also exhibit low immunogenicity and higher stability, reducing unwanted mutations. Unlike nonviral cDNA vectors, BACs allow for spatiotemporal gene regulation, closely mimicking natural gene function. Additionally, recent advancements in homologous recombination techniques have simplified BAC modifications, making them a powerful tool in genetic engineering, functional genomics, and disease modeling.

Conclusion:

Bacterial Artificial Chromosomes (BACs) are essential tools in genetic research, enabling the cloning and stable maintenance of large DNA fragments. With their high stability and low mutation rate, BACs have been widely used in genome sequencing, mapping, and disease studies, playing a crucial role in the Human Genome Project. Strengthen your NEET preparation with Vedantu’s expert study material. Start learning now.

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