One of the most striking conclusions from the completion of the human genome sequence reported by both public and private consortia earlier this year was the surprisingly low total number of genes -— about 30,000. This led to some dramatic changes in thinking about the way in which the human genome is organized.
However, in this week's issue of Cell, Michael Cooke and colleagues present an analysis suggesting that these initial estimates of the gene number were too small.
Cooke and colleagues compared the identified genes in both genome sequences with each other and also with a third database of gene sequences, called Refseq.
They found surprisingly little overlap between the identified genes in the two reported genome sequences.
Only about half of the genes found by either sequence consortium matched genes found by the other group. Thus, if added together, the overall number of identified genes is significantly higher than either group concluded.
Cooke and colleagues confirmed that representatives from the different groups are in fact functional genes by showing that they are expressed in at least one type of human tissue.
The overall conclusion is that the total number of human genes is substantially higher than the 30,000 deduced from the initial genome sequence publications.
This follows a trend set by other genome sequences, such as Drosophila, where current estimates of the gene tally are higher than the initial ones. Among the reasons for these changing estimates are the improving quality of the sequence data and better computational methods used for analysis.
While the new study does not provide a definitive answer to the question of how many genes humans have, it appears that the previous conclusions about the low number of human genes were premature.
(Reference: Cell Volume 106 Number 4 August 24, 2001)
[Contact: Mike Cooke]
24-Aug-2001
