One Gene, Two Genes, Three Genes, Four: Scientists Wonder How Many More

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When you were a kid, did you ever try to win a prize by guessing how many jelly beans were in the big jar? Is it 500? 5,000? Hard to tell when the numbers get so high.

If you have played this kind of guessing game, the Cold Spring Harbor (N.Y.) Laboratory’s Genesweep will probably seem familiar. But instead of a pile of candy, the guesses aim at a basic question about the foundations of human life: How many genes make up the human genome?

The contest was organized by Ewan Birney, Ph.D., of the European Bioinformatics Institute in Cambridge, England, at CSHL’s genome conference in May, where the topic reportedly was “hotly debated.”

Now that the genome’s 3 billion DNA base pairs have been sequenced, can’t scientists just count the genes? Well, no; it is not quite that simple.

When a simple organism’s genome is sequenced—a bacterium or yeast, for example—it is relatively easy to identify the genes because they make up most of the organism’s DNA. For these creatures that reproduce fast and die young, evolution has ensured that the Biology 101 axiom—DNA makes RNA makes protein—works in a highly efficient and mostly straightforward way.