Researchers studying infectious diseases, such as AIDS, may be able to find answers more quickly thanks to a new tool that lets them see how a Rhesus monkey's 20,000 genes respond.

That tool, called a gene chip or microarray, was developed with the help of researchers at the University of Nebraska Medical Center in roughly half the time and cost of previous gene chips of humans and mice, said John Harding, with the National Center for Research Resources at the National Institutes of Health.

The gene chip for the Rhesus macaque monkey will be especially useful because the genetic code of the monkey is similar to humans, and many experiments cannot be performed on humans because of ethical concerns.

"This is very definitely an important project, and it's going to help us tremendously," said Shrikant Mane, a researcher at Yale University who has analyzed human gene expression and he helped identify the gene for macular degeneration.

Robert Norgren led researchers at the University of Nebraska Medical Center in Omaha who worked on the Rhesus macaque monkey project over the past 2½ years.

The Rhesus gene chip, which is marketed by a California company named Affymetrix, allows scientists to see all of the genes at once and look for patterns in which genes are "turned on" and "turned off," Norgren said. Affymetrix started selling the Rhesus gene chip this past summer.

The pattern of which genes are active offers clues to possible treatments and ways to interfere with the progression of diseases, Norgren said.

And they can help scientists determine how well vaccines and treatments work.

Before gene chips were perfected in the last few years, Norgren said scientists had to study genes individually to see how they responded, which made it difficult to determine patterns.

The Rhesus gene chip will be useful to researchers studying infertility and neurobiology as well as infectious diseases.

Mane said it is always a struggle to obtain human samples to study in neurobiological research, so being able to conduct experiments on monkeys will be helpful.

"It's definitely going to help with clinical trials," Mane said.

A $2.25 million grant from the National Center for Research Resources that Harding oversaw paid for the work.

Norgren used preliminary research done at Baylor University in Waco, Texas, to identify many of the Rhesus genes. Baylor is working sequencing the full Rhesus genome, but that project is still five to 10 years from completion.

Norgren targeted his research on the genes that had not been identified by Baylor, and he paid particular attention to Rhesus genes that are most similar to humans. Norgren said his team sequenced about 5,000 genes.

Harding, who is director of primate resources at the National Center for Research Resources, commended Norgren's work, which was described in an article published online this month in the BMC Genomics journal.

"He could do a very directed attack, and that was very cost effective," Harding said.

One side benefit of this gene chip, Norgren said, is that fewer Rhesus monkeys will be needed to get reliable results in future research.