WASHINGTON, March 29 – Eric Lander, director of the Center for Genome Research at MIT's Whitehead Institute, on Thursday defended the Human Genome Project's assertion that a few hundred genes appearing in the human genome were horizontally transferred from bacteria to a vertebrate ancestor.
This hypothesis was advanced in the paper "Initial Sequencing and Analysis of the Human Genome," published in the February 15 issue of Nature , to explain why 223 genes were found in vertebrates and bacteria but not in non-vertebrate eukaryotes including yeast, mustard weed, fly, and worm.
Since the paper’s publication, GenomeWeb has reported that other scientists have disputed the claim, including Steven Salzberg of The Institute for Genomic Research and Russell Doolittle of the University of California at San Diego. They suggested that the software tools used to detect homologies between the human and lower eukaryote genes may not have been sensitive enough to pick up those with a high mutation rate.
Speaking Thursday at a seminar on "The New Biology: Challenges and Opportunities," held by the Center for Strategic and International Studies in Washington, Lander acknowledged that there may be more than one answer. "The creative process of making genes is really quite varied," he said.
While Lander's team favors horizontal transfer of genes between bacteria and vertebrates as the explanation for most of the 223 genes in question, he told GenomeWeb that he would not be surprised if some of the genes were actually present in eukaryotes that have not yet been sequenced. This would imply that the gene existed in a common ancestor, but was shed at some point during the evolution of the organisms the scientists happened to study.
"Our view of phyla is so limited. One organism stands for them all. We say 'fungi don't have something', when what we mean is S. cervisiae doesn't have it. We should be doing survey sequencing of many organisms," Lander said.