More Genes than We Thought?

Sept. 25, 2001

When the human genome was published, it was stated that humans had only 30,000 to 40,000 genes, much fewer than previously thought. Two teams both came up with this estimated number of genes. This was surprising because the lowly fruit fly has only about 13,600 genes. The small flowering plant Arabidopsis thaliana has about 25,000 genes. Initial estimates for the number of genes in humans were in the range of 80,000 to 100,000 genes.

Now it turns out that the number of genes may not be known, after all. In an article published in the journal Cell in August, 2001, the results of the two teams were compared, and as reported in an article in MSNBC, August 23, 2001,

a team lead by Dr. Michael Cooke of the Genomics Institute of the Novartis Research Foundation in San Diego compared the two groups' findings and found out that they had identified two quite different sets of genes, with only roughly a 50 percent overlap between them.
The two groups agreed on the existence of about 17,000 genes. But about 25,000 more were found only by one group or the other. "It's a jaw-dropper," said Cooke, whose findings are published in Friday's issue of the journal Cell.

This means that one of the groups identified only about half of the genes found by the other group. Assuming that the same percentage of the total number of genes was found, this would mean that the number of genes possessed by humans is about 60,000, and it could be even higher. It is also possible that only the 17,000 genes found by both groups are genuine, in which case the total number of genes could be very small.

At any rate, it is too soon to say that the human genome has been decoded. Perhaps more caution on the part of the human genome project participants is warranted.

Back to home page.