Well, maybe not many more than it takes to make a small plant. That's the rather humbling indication, anyway, from some recent estimates for one of the most basic numbers in biology. That compares pretty impressively to the 25,500 genes in the small flowering plant called Arabidopsis thaliana or thale cress. And it towers comfortably above the 19,000 genes in the tiny worm C. elegans or the 13,600 genes in the fruitfly Drosophila.
Scientists still disagree wildly on the human gene number.
Their formal betting pool records estimates from 27,462 to 153,478 genes, with an average of about 62,000. Human Genome Sciences Inc. of Rockville, Md., for example, puts the number above 120,000, based on analysis of chemical instructions from genes for making proteins. But recently, the leader of the international project that has completed a rough draft of the human genome said he expects the gene inventory to fall between 30,000 and 40,000. And last June, in the journal Nature Genetics, two teams of scientists independently presented studies with estimates in the range of 28,000 to 35,000 genes. People may find numbers like these disquietingly close to the totals for the Arabidopsis plant or the C. elegans worm.