When the Chips are Down
- Physicians World Communication Group, Secaucus, New Jersey 07094 USA
This extract was created in the absence of an abstract.
Mini revolutions in DNA technology began with the structure of the double helix. Several major advances over the last 45 years include restriction enzyme mapping, DNA sequencing, and PCR. Each advance generated much excitement, and its importance was recognized by the Nobel Prize. And now, once again, DNA technology has made a quantum leap.
Even a few years ago it would have seemed preposterous to suggest that DNA analysis could be carried out on a thumbnail-sized glass chip. But that is exactly what is happening in several laboratories and biotechnology companies around the country. The brainchild of Stephen Fodor (President and Chief Executive Officer of Affymetrix with headquarters in Santa Clara, CA), the GeneChip, introduces the idea of parallel genomics—the marriage of two disciplines: biotechnology and semiconductor manufacturing. As excitement in the wonders of this technology mounts, an increasing number of university laboratories and several biotechnology companies are anticipating the needs of the experimenter by preparing to offer competing technology. Hopefully, this will allay the fears many scientists have of finding this technology inaccessible and ultimately unaffordable.
The Technology and its Cost
At Affymetrix, an independent company spun out of Affymax in 1991, the technique of photolithography as a method for synthesizing peptides on a solid support was adapted for nucleic acids (see Box 1).
Box 1
Methods for Creating a DNA Array
Photolithography: The first step is manufacturing a GeneChip probe array. Affymetrix’s gene chip assembles a series of DNA probe arrays of known sequence on a glass wafer using repeated cycles of photolithography. A combinatorial array of known DNA sequences is thus manufactured at specific sites on the chip. In the next step a fluidics station automates the hybridization of the array with the target DNA marked with a fluorescence tag. The times, temperatures, and stringency of hybridization are controlled in …
