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Overlooked: 137 new yeast genes revealed


Imagine the frustration of trying to finish an incredibly complex jigsaw puzzle that is marred by a few blank pieces. That's the sort of problem faced by researchers who are trying to identify every gene in the 'fully sequenced' genomes of organisms.

Now Yale University researchers have developed a more systematic approach to filling those missing puzzle pieces. They found 137 genes that had been previously overlooked in the genome of the yeast Saccharomyces cerevisiae. This is more than twice the total number of yeast genes identified during the four years following the completion of the S. cerevisiae genome in 1997.

"The majority of these new genes are either short or overlap a previously annotated gene on the opposite strand" of DNA, write Michael Snyder and colleagues in Nature Biotechnology. They reported that 15 of the new genes were discovered within the sequences of other known genes, and 75 percent of the newly identified genes were shorter than what scientists had expected to be the minimum length.

The researchers discovered those elusive genes using a systematic step-by-step approach that may help other scientists do similar analyses of organisms with larger genomes. First, they tagged genome segments with foreign DNA sequences and applied staining techniques to identify potential new genes in those sections. Then they used microarray analysis to check whether the suspected new sequences actually coded for genes. Finally, they screened what appeared to be new genes against existing databases of other organisms' genomes, looking for matches that hint at how the sequences function.

While the Yale researchers concede that even their systematic approach may have missed many other yeast genes, they also think that a number of the previously identified genes many prove to be spurious: "We predict the presence of ~ 400 spurious yeast genes to be offset by the presence of an equal number of previously unappreciated genes, yielding a stable total population of ~ 6,000 genes in yeast," they write.

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Kumar, A. et al. An integrated approach for finding overlooked genes in yeast. Nature Biotechnol 20, 58-63 (January 2002).

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