New Genes Found on Chromosome 21

Use of refined analytical techniques has revealed that human chromosome 21 contains roughly 10% more genes than were previously either predicted or confirmed. The missing genes were likely not identified before because they are small and encode small proteins. This finding is reported in the June 2002 issue of Genomics.

"This demonstrates why we cannot rely on gene prediction alone to identify all human genes,” said the study's lead author, Dr. Stylianos Antonarakis of the University of Geneva Medical School (Switzerland). "Getting the right number of genes is crucial if we hope to use this information to fight disease.”

The initial DNA sequence of chromosome 21 showed 127 known genes, and another 98 were predicted. In the current study, researchers analyzed chromosome 21 through a strategy that compares the genome sequence with experimental data generated from expressed sequence tags (ESTs). Taken from various tissues or cell types, EST transcripts provide strong evidence that a portion of the genome is actually expressed and functions as a gene. This approach identified a number of suspected new genes on chromosome 21. Further analytical tests including gene mapping confirmed this data. All told, the researchers identified 163 genes known to exist on chromosome 21 while discovering 19 new ones.

"The initial "road map” of the human genome has been extraordinarily important for pointing everyone in the right direction, but we are finding a lot of room for errors,” said Dr. Antonarakis. "A more accurate map will require a gene-by-gene search that needs to be followed up with thorough testing.”



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University of Geneva Medical School