New research reveals that humans have fewer genes than thought
Next month, a first draft of the human genome is expected to be published, but scientists are still not sure how many genes actually make it up. When geneticists are asked how many genes a person has, they usually point to a number ranging from 80 to 120 thousand. However, two weeks ago a team of scientists from Europe and the United States finished deciphering the genetic code of chromosome number 21, and announced that based on the number of genes found on it and on chromosome number 22 (its analysis ended in December), humans only have about 40 genes.
Since the publication, the number of human genes has become a hot topic. A resourceful scientist, Evan Birney of the European Bioinformatics Institute, even founded a betting contest on the website www.ensembl.org/genesweep html.
These are the rules of the competition: each bettor pays one dollar and submits his bet regarding the number of genes in the human genome. In 2003 - when the human genome is expected to be almost completely deciphered - geneticists will have a much more accurate estimate of the number of genes. The gambler who guesses the number closest to the real number of genes will win the entire jackpot, and a leather-bound copy of the book "The Double Helix" signed by the author James Watson, discoverer of the DNA double helix structure.
At a recent conference in New York, the scientists leading the project to decipher the human genome laid out their stakes. For example, Francis Collins, head of the genome project at the National Institute of Human Heredity in the United States, estimated the number of genes at 48,011. When Eric Lander, head of the Whitehead Institute, who deciphered about a third of the human genome, was asked why he bet on the number 47,317, he said, "Actually, I already forgot what my bet was. The truth is that all the bets were made at the bar, someone passed by with a piece of paper and collected the bets from everyone."
Why does it even matter how many genes there are in the human genome? If the genome is likened to the genetic instruction book of all life, then the genes are the words. Apparently, it can be assumed that small creatures have a short "genetic book", and complex creatures, such as humans, have a large genetic book. However, the knowledge accumulated so far shows that this assumption may turn out to be simplistic. The team that recently deciphered the genome of the fruit fly discovered that the fly has about 5,000 genes less than the nematode worm, which is considered a simpler organism. "Biological complexity is probably not determined by the number of genes, but by their activity and the interrelationships between them," says Lander, who arrived in Israel the other day to receive an honorary doctorate from Tel Aviv University.
Three studies will be published in the June issue of the journal "Nature Genetics". According to two of them, the number of human genes ranges from 27 to 34 thousand. In contrast, the third study concluded that humans have about 120 genes. However, other researchers have argued that the third estimate is based on the wrong scale.
{Appeared in Haaretz newspaper, 23/5/2000}
