DNA chip

DNA chip is a popular name for oligonucleotide? probe microarray?, a technique used in molecular biology, especially genetics, to quickly scan a large DNA strand, or even a whole genome, for mutations.

Procedure

A DNA strand of known sequence (for example, a gene) is cut by restriction enzymes into short fragments (called oligonucleotides). These fragments are then tagged with a fluorescent chemical (for example, a red one), denatured into single strands, and fixated on a chip at regular intervals.

To check another gene of the same kind for mutations, it is cut into fragments the same way as the "clean copy" has been. The fragments are tagged with a different fluorescent chemical (for example, a green one), denatured into single strands, and applied to the prepared chip.

The unmutated fragments of the tested gene will anneal to (or hybridize? with) the fragments on the chip, showing the spot in both red and green fluorescence. Fragments that carry a mutation will not anneal to a fragment on the chip, leaving the spot red.

Applications

There are many applications for DNA chip technology, not only in molecular biology, but also in medicine. Some examples are :

• Genome check for microorganisms. There are chips that contain the complete [E. coli]? genome; interesting E. coli phenotypes can be quickly screened? for mutations using DNA chips. Anyone knows if there's a yeast chip yet?
• [Hereditary disease]? check. Humans can be tested for mutations in genes that are known to lead to hereditary diseases. This can be important for diagnosis? and therapy, as well as for screening the parents to determin the risk of a child for such diseases.

Economics

Although the technique is relatively new, its advantages are already creating a notable demand on the biotechnology sector. There are companies that produce DNA chips for the special needs of their customers. Today (2001), a single DNA chip costs between $100 and $400, but is expected to become much cheaper ($5-$20) within the next few years.

See also :

External links : http://www.devicelink.com/ivdt/archive/98/09/009.html Basics, some nice images.