Bacterial artificial

November 12, 2012

Bacterial artificial

In order to analyze the DNA sequence – and specifically in the human genome sequencing – scientists used bacterial artificial chromosomes. Using this method is one way in which sufficient material for analysis can be found.

The bacterium known as Escherichia coli – or E. Coli which is familiar to many as the source of food poisoning outbreaks – is responsible for the production of the plasmid used to create the cloning method involved in bacterial artificial chromosomes. The use of bacterial artificial chromosomes means that it is possible to examine repeatedly expressed foreign DNA which will have produced many copies in the cells of the bacteria thus facilitating DNA analysis. The E. Coli plasma used in this process is the F plasmid; this allows connection and exchange of DNA between two bacteria. This means that the bacterial artificial chromosomes will contain genetic information from this conjugation as well as the DNA required for incorporating into the bacterium. The use of sequence tag connectors means that once the bacterial artificial chromosomes is incorporated into the E. Coli it is then possible to identify the already inserted foreign DNA.

This process means that the amount of DNA which can be examined can be substantial, the use of bacterial artificial chromosomes means that it is possible to use large stretches of DNA within the bacterial genome and then replication will included both the foreign DNA and the bacterial.

Since their development in 1992 the usefulness of bacterial artificial chromosomes has grown apace. The use of BACs gives stability to the DNA which is inserted into the bacteria where it will remain during repeated cycles – therefore information is not lost. It is also to its advantage that the normal tools of molecular biology are sufficient tools for the sequencing of bacterial artificial chromosomes.

In the sequencing of the human genome the use of BACs increased the speed of the process and also reduced the cost. This is due to a technique known as ‘shotgun cloning’ where many fragments of human DNA were incorporated into the bacterial artificial chromosomes, expressed into the E. Coli in order for sequence determination to take place – the sequences were then reconstructed in the correct sequence.

To date almost 1 million fragments of human DNA have been used in this way. Research has moved into other areas including the sequencing of corn and rice which are agriculturally important plants and also the mouse. The use of BACs have meant giant leaps forward in screening for genetic abnormalities – cloning kits have been developed using bacterial artificial chromosomes and are available commercially for genomic profiling.

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