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Thread: Scientists Question Report on Genes

  1. #1

    Scientists Question Report on Genes

    .c The Associated Press

    BOSTON (AP) - Scientists are questioning the most surprising discovery from last winter's deciphering of the human genetic code - the assertion that people have only about 30,000 genes, or roughly twice as many as the fruit fly.

    A new analysis suggests that number is too low, and the real total could be considerably bigger. However, researchers who came up with the original figure are sticking with it, at least for now.

    Scientists have long argued over how many genes it takes to build a human. Educated guesses have ranged up to 150,000.

    The issue seemed settled last February, when two competing scientific teams published the first detailed look at virtually the entire library of genetic information contained in every human cell.

    Both groups laid out the 3 billion bits of data that make up the code. Both used computers to distinguish the information that is genes from the look-alike filler. And both came up with roughly the same estimate: between 30,000 and 40,000 genes, with the best bet under 35,000.

    Some speculated that the relatively small number of human genes was good news, because it means less work to understand how they all work and perhaps translate that information into cures and treatments for various diseases.

    To many scientists, the fact that the two groups independently arrived at the same number made it believable.

    However, a team lead by Dr. Michael Cooke of the Genomics Institute of the Novartis Research Foundation in San Diego compared the two groups' findings and found out that they had identified two quite different sets of genes, with only roughly a 50 percent overlap between them.

    The two groups agreed on the existence of about 17,000 genes. But about 25,000 more were found only by one group or the other.

    ``It's a jaw-dropper,'' said Cooke, whose findings are published in Friday's issue of the journal Cell.

    Just how many genes it takes to construct a human is unclear from the latest analysis. While Cooke believes 30,000 is too low, he estimates the total is probably not more than 60,000.

    For now, nobody knows how many genes were missed by both teams or how many of those identified by just one group truly are genes.

    One catalog of genes was compiled by Celera Genomics of Rockville, Md., the other by an international consortium headed by the National Human Genome Research Institute.

    Officials of both Celera and the consortium contend that most of the 25,000 genes found by just one group or the other will turn out to be phonies, so the final answer may still be somewhere around 30,000.

    ``It's way too simplistic to say you can add up the non-overlapping sets and get a bigger number,'' said Celera President Craig Venter. ``They're probably bogus.''

    Dr. Francis Collins, head of the genome institute, agreed the total is unlikely to grow hugely. ``It would not stun me if there turned out to be 50,000,'' he said. ``It would stun me greatly if there were 100,000.''

    Dr. Gerald Rubin, a fruit fly expert at the University of California at Berkeley, said some scientists suspected all along that the total number would turn out to be higher than 30,000. His guess: Humans will have 54,000 genes, or four times more than the 13,600 in the fruit fly Drosophila.

    Scientists are running a betting pool on what the total will be, and so far 165 have entered. (The cost of a bet rose from $1 to $5 after the release of February's data.) Right now, their average guess is 61,710 genes. The winner will be chosen in 2003, by which time it is hoped the answer will be clear.

    Collins' bet, made two years ago, was 48,011. ``I'll hold on,'' he said. ``I'm not completely retracting that.''

    On the Net:


    Betting pool:

    AP-NY-08-23-01 1701EDT

    What's your bet Dr Young?

  2. #2
    Most genes code for only part of a protein complex. Many genes simply regulate other genes. Some genes are redundant. Some genes may not be expressed very much, if at all. Soon, the question will arise what a gene is?


  3. #3

    Human Genome Now Appears More Complicated After All

    August 24, 2001

    Human Genome Now Appears More Complicated After All


    fter a humiliating deflation this February, human dignity is on the recovery path, at least as measured by the number of genes in the human genome.

    Two new estimates put the likely number of human genes at around 40,000, up by a third from the estimate of about 30,000 in February by the two teams of scientists who decoded the human genome. The low estimate still has its defenders.

    The 30,000 number suggested that evolution had not found the design, operation and maintenance of a person much more complicated than the job of running the microscopic round worm (19,000 genes), the fruit fly (13,000 genes) or the mustard cress plant (25,000 genes), the three other multicellular organisms whose genomes have been analyzed.

    Until the human genome was decoded, the textbook �gure for the number of human genes had been 100,000, putting a safe distance between people and the little creatures on which the genome decoding methods were �rst tested.

    But 100,000 was just a guess. When the 3.2 billion letters of the human genome were decoded, computer programs set to analyze the sequence found that 1 percent of the DNA consisted of genes. Both the government-�nanced consortium of academic centers and its rival, Celera Genomics of Rockville, Md., concluded there were 30,000 or so well- documented genes, though both allowed that the number might grow.

    Dr. Michael P. Cooke, Dr. John B. Hogenesch and colleagues at the Genomics Institute of the Novartis Research Foundation in San Diego have now compared the two sets of human genes from Celera and the consortium, �nding that 15,000 genes are common to both. The fact that the two sets do not entirely overlap has not been generally known.

    Based on a test of their own, the Novartis biologists believe that most of the genes found by Celera alone, and by the consortium alone, are real. If all the human genes found by only one of these groups are added to the 15,000 found by both, the total comes to around 40,000.

    Dr. Cooke said his next project was to test whether all 40,000 of these predicted human genes were real.

    Separately, Dr. Christopher Burge of the Massachusetts Institute of Technology said he had an article in the journal Genomics suggesting that the total number of human genes was around 40,000. Dr. Burge is the author of Genscan, one of the principal programs for predicting which regions of the genome contain genes.

    Dr. Cooke and Dr. Hogenesch said they were less interested in the precise number of human genes than in making sure they had the full set, however many it might be, since researchers trying to understand some aspect of the body's function could be led astray if some vital gene was missing from the catalog.

    The importance of cataloging every human gene is to understand how human cells work in health and disease and to devise gene-based remedies for many ailments.

    The number of genes dictates the size of that task, since it would presumably take longer to understand the roles of 40,000 than of 30,000. Obtaining the precise number is also a test of how well biologists understand the human genome.

    Now that the number may be ascertainable, biologists are being more cautious in their predictions.

    "People were throwing numbers around, and now there is complete silence on the subject," said Dr. Burge, suggesting there was a fear of looking foolish with the wrong estimate.

    In May last year, with estimates of the number of human genes ranging all over the lot, scientists meeting at the Cold Spring Harbor Laboratory on Long Island organized a sweepstakes for bets on the exact tally, with the winner to be chosen in 2003.

    It is now not so clear that the real number of human genes will be known any time soon. With all the estimates out there, "it has to be becoming clear to people it must not be simple," said Dr. J. Craig Venter, the president of Celera Genomics.

    Dr. Venter said that the Novartis scientists were the �rst to point out publicly that Celera's predicted set of human genes and that of the public consortium did not overlap much, a fact that means the consortium "has missed a lot."

    Dr. Eric Lander, chief author of the consortium's report, was traveling and unavailable for comment.

    Dr. Venter said he disagreed with the Novartis scientists' method and did not plan to revise his tally of 26,000 well-documented human genes. He also found other more doubtful ones, and with further research his number could go up or down by 5,000 genes.

    "It will probably take 5 or 10 years to have a really accurate count plus or minus 100 genes," he said.

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