March 7, 2002 | The human genome became that much more accessible in January when Affymetrix unveiled its new U133 Human Genome GeneChip set. Squeezing essentially all of the human genes onto a pair of DNA microarrays has both symbolic and more practical implications.
The company’s last human genome offering was a collection of five chips (U95) housing an estimated 60,000 sequences; however many were poorly characterized expressed sequence tags (ESTs)-fragments of expressed genes. The new dual-chip set takes advantage of the nearly complete genomic sequence, and targets 33,000 of the “best characterized” genes- a number that closely resembles current estimates of the total number of human genes.
“With the U95 set, it seemed that many of the ESTs on the chips probably did not represent distinct and different genes,” says geneticist Eric Hoffman, from Washington, D.C.’s Children’s National Medical Center, one of the nation’s largest gene expression profiling groups. Hoffman hopes the new chip will be “faster, cheaper, better,” and he points to the recent release of the sequence of every dot on the U133 chips, facilitating comparisons between generations of arrays. “This has delighted the academic community,” says Hoffman.—Malorye A. Branca