Structural Biochemistry/DNA recombinant techniques/Artificial Chromosomes

General Information
Artificial chromosomes are synthetic chromosomes consisting of fragments of DNA integrated into a host chromosome. These artificial chromosomes are introduced into host cells to propagate and can be used to transfect other cells, introducing new DNA. Artificial chromosomes are useful in cloning larger fragments of DNA, as plasmids can only contain up to 10,000 base pairs and phages are hard to work with. Artificial chromosomes can contain anywhere from 300,000(BAC) to 1,000,000(YAC) base pairs, effectively reducing the amount of runs needed for a large fragment to be analyzed. Because these chromosomes are more useful in cloning larger fragments of DNA, it is easier and quicker to clone and transform genes. Artificial chromosome vectors also make it easier to store through bacterial cells rather than mammalian cells.

There are two types of artificial chromosomes: Bacterial artificial chromosome (BAC) and yeast artificial chromosomes (YAC). Although yeast artificial chromosomes can contain more base pairs (over one million) than bacterial artificial chromosomes, bacterial artificial chromosomes are more common than yeast artificial chromosomes because they are more stable, making them easier to work with a smaller risk of rearrangement due to the circular shape of a plasmid. Yeast artificial chromosomes also may produce chimeric effects, while bacteria artificial chromosomes will not.

The usage of artificial chromosomes is mainly for studying DNA fragments. This is done by integrating a non-viral/non-bacterial DNA into a bacterial chromosome and having it express the DNA fragment within the host. Once expressed, the host cell undergoes replication and thus the host chromosome containing the integrated DNA fragment will be replicated. The result is a huge colony of bacteria containing the fragmented DNA. In other words the DNA is cloned into millions of copies. The use of artificial chromosomes has revolutionized every aspect of biological studies.