Humans Have Fewer Genes Than Previously Thought

A more refined analysis of the human genome shows that people have fewer genes than originally believed, according to researchers working on the Human Genome Project, a publicly funded collaboration of scientists from 20 institutions in the United States, Europe and Asia.

The new number is 20,000-25,000 genes.

“Only a decade ago, most scientists thought humans had about 100,000 genes. When we analyzed the working draft of the human genome sequence three years ago, we estimated there were about 30,000 to 35,000 genes, which surprised many,” said Francis Collins, the director of the US National Human Genome Research Institute in Bethesda, Maryland.

“This new analysis reduces that number even further and provides us with the clearest picture yet of our genome,” he added in a statement.

“It’s important to let people know that there is an even better reference sequence out there for the human genome,” Dr. Jane Rogers, head of sequencing at the Wellcome Trust Sanger Institute in England, which worked on the project, said in an interview.

The refined sequence reported in the October 21st issue of Nature is the most complete so far. It covers 99% of the gene-containing parts of the human genome, identifies 99.7% of known genes and is 99.9% accurate, according to the scientists.

Because it is so complete it will improve the search for genetic causes of disease. Scientists also expect it to advance drug development by customizing treatments to genetic profiles.

The refined sequence identifies the emergence of 1,183 genes in the last 60-100 million years and the suppression of about 30 genes in a similar period.

Dr. Rogers said now that researchers had a refined sequence of the human genome, they needed to learn more about how genes are regulated and used.

Nature 2004;431: 927-945.