Competing maps of the human genome are being laid bare this week as scientists hurry to tell the world what treasures lie buried in the long, complex chain of human DNA.
Like pirates” maps spread out on a sandy beach, with exciting details on view for the first time, the genetic data offer intriguing clues to how life operates, where we came from, and how we got here.
“This turns all the lights on now,” molecular biologist Richard McCombie said yesterday at the Cold Spring Harbor Laboratory in New York, who is a key player in the publicly financed Human Genome Project. Now, “you can see everywhere” in the human set of genes, and “we”ll be forced to ask bigger questions.”
University Prof. Francis Collins, head of the public project, added: “There are some stunners here.” For example, far fewer genes have been found than expected. “We thought we were big, fancy, complicated organisms. But our gene-list is a lot less impressive than we expected. That”s quite a surprise.”
The main surprise is that the human genome is rather small, containing only about 30,000 to 40,000 genes, rather than the anticipated 100,000-plus.
University genetics Prof. Miriam Meisler said despite the fact that fewer genes were discovered than originally anticipated, many of them remain a mystery to scientists.
“We want to determine the function of genes that are completely unknown,” Meisler said. “That”s a big goal for the next 10 years, to assign function to the genes we don”t know about yet.”
Although finding fewer genes means there”s less to look at, it also means that the genes are more complicated than expected. The low gene number overturns the cherished idea that each gene has only one function. Instead, it appears that each gene makes perhaps three or more proteins, and scientists must sort out just how that is done.
The first analyses of the human gene set are being published by the Human Genome Project in Thursday”s issue of the British journal Nature. The competing version of the genome according to Celera Genomics Inc., the private gene-chasing company will appear Friday in Science, the journal of the American Association for the Advancement of Science. Details of both were announced yesterday.
“There are a lot fewer genes than anyone expected,” said mathematician/ geneticist Eric Lander, a leading researcher at the Whitehead Institute in Cambridge, Mass., and first author on the Human Genome Project”s report. “The implications are important, because it means there are many fewer genes that need to be characterized.”
Celera also announced yesterday that the mouse genome has been deciphered an important step, because the human and mouse genomes are similar in size and function, and can now be compared gene-by-gene. Because the mouse is so useful in experiments, the function of human genes can be inferred by testing all the mouse genes.
McCombie said when genome research “gets into the mouse, then it”s just going to explode” with exciting new research results. Human diseases can be mimicked, drugs can be tested, and treatments can be devised.
Meisler, who is working on the sequencing of the mouse genome, said the similarity between the two provide important comparisons.
The functional genes in a mouse are 85 percent the same as the functional genes of humans, Meisler said, while the nonfunctional genes are less than 50 percent the same. This means that the mouse genome can help identify the functional parts of the human genome.
An added advantage of the mouse genome is the ability to experiment in ways that can”t be done on humans, Meisler said.
But the main discovery that humans have fewer genes than expected (Celera says 26,000 to 39,000 the public consortium, 30,000 to 40,000) is important because the body”s proteins are all created via instructions in the genes, and now there seem to be more proteins than there are genes. A gene”s chemical code specifies which building blocks amino acids get strung together in specific arrangements to make different proteins.
So how might a single gene make more than one protein? One suggestion, Lander said, is that “there is more mixing and matching of parts” during protein-building than was expected. It now seems that the proteins vital for life “are put together in a richer set of combinations,” Lander said.
As a result, “we get more out of our proteins than others” such as fruit flies and worms do, and “that was unexpected, a real surprise,” Collins said.