Evolutionary comparison finds new h...( Using supercomputers to compare port...)

Using supercomputers to compare portions of the human genome with those of other mammals, researchers at Cornell have discovered some 300 previously unidentified human genes, and found extensions of several hundred genes already known.

The discovery is based on the idea that as organisms evolve, sections of genetic code that do something useful for the organism change in different ways.

The research is reported by Adam Siepel, Cornell assistant professor of biological statistics and computational biology, Cornell postdoctoral researcher Brona Brejova and colleagues at several other institutions in the online version of the journal Genome Research, and it will appear in the December print edition.

The complete human genome was sequenced several years ago, but that simply means that the order of the 3 billion or so chemical units, called bases, that make up the genetic code is known. What remains is the identification of the exact location of all the short sections that code for proteins or perform regulatory or other functions.

More than 20,000 protein-coding genes have been identified, so the Cornell contribution, while significant, doesn't dramatically change the number of known genes. What's important, the researchers say, is that their discovery shows there still could be many more genes that have been missed using current biological methods. These methods are very effective at finding genes that are widely expressed but may miss those that are expressed only in certain tissues or at early stages of embryonic development, Siepel said.

"What's exciting is using evolution to identify these genes," Siepel said. "Evolution has been doing this experiment for millions of years. The computer is our microscope to observe the results."

Four different bases -- commonly referred to by the letters G, C, A and T -- make up DNA. Three bases in a row can code for an amino acid (the building blocks of proteins), and a string of these three-letter cod
'/>"/>