SCIENCE IN THE NEWS - Genetic Map of Chimps May Show What Ma（在线收听）

SCIENCE IN THE NEWS - Genetic Map of Chimps May Show What Makes Us Human
By George Grow, Cynthia Kirk and Jerilyn Watson

Broadcast: Tuesday, September 20, 2005

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This is SCIENCE IN THE NEWS in VOA Special English. I'm Barbara Klein.

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And I'm Bob Doughty. This week, we tell about a possible new use for American alligators. We also will tell how some American scientists have reacted to a report critical of homeopathic treatments.

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But first, a genetic map of an animal may show what makes us human beings.

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Scientists say people and chimpanzees developed separately since they split from a common ancestor about six million years ago. But studies have shown that chimpanzee genes are very similar to those of human beings.

Recently, an international team of scientists said it has prepared a partial genetic map of a chimp. They found that ninety-six percent of the chimp genes are exactly the same as human genes. Scientists say the remaining four percent may help to explain what makes humans different from chimps. They also say knowing the genetic differences may prove useful in medical research.

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Studies of D.N.A. make it possible to understand the genetic relationships of all life on Earth. The letters D.N.A. represent deoxyribonucleic acid. Every cell of every living thing contains D.N.A. Scientists call it the chemical of life. All of the D.N.A. in cells is called the genome.

D.N.A. is made up of genes. Genes, like letters in words, carry a huge amount of information. These messages tell cells how to make all the materials for life.

Genes are carried on chromosomes. Almost all human cells have forty-six chromosomes. There are hundreds of genes on each chromosome. The chemicals that make up D.N.A. are nucleic acids. There are four kinds of nucleic acid: adenine, thymine, guanine and cytosine. These chemicals are called bases. They are represented by the letters A, T, G and C.

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Robert Waterston is the head of the Department of Genome Sciences at the University of Washington School of Medicine in Seattle, Washington. He directed the Chimpanzee Sequencing and Analysis Consortium Project.

America's National Human Genome Research Institute provided assistance for the study. The findings were reported in the two publications, Nature and Science.

Professor Waterston and his team studied the D.N.A. of a chimpanzee named Clint. Clint lived at the Yerkes National Primate Research Center in Atlanta, Georgia, until he died of heart failure last year.

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The team of scientists made a map of the position of every one of Clint's genes. It then compared the chimp genes to the human genome. Human chromosomes have about three thousand million D.N.A. base pairs. Chimpanzees have about the same number.

The scientists found that only forty million base pairs differ between human and chimp. They say this means a generally small number of genetic differences are responsible for differences between people and chimpanzees. They also say the number of genetic differences between human and chimp is about ten times more than between any two persons.

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Professor Waterston and his team compared genes that control the activity of other genes. They found that the genes had changed quickly in human beings, but not in chimps.

Professor Waterston says the study strongly confirms the theories of the British nature scientist Charles Darwin. Darwin developed the theory of evolution that life on Earth developed through a process he called natural selection.

A separate study published in Science examined gene activity in chimpanzees and humans. That study found that genes common to both appeared to have become more active in the brains of humans. But the activity of shared genes in the heart and other organs remained the same.

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A large animal that lives in America's southern wetlands may provide a valuable substance with medical uses. American scientists are exploring ways to help people with collagen removed from dead alligators.

Jack Losso and Mark Schexnayder work for the agriculture center at Louisiana State University. They are the lead investigators on the alligator collagen project.

Collagen is the most important protein in connective tissue. It holds cells together. It helps form bone and cartilage, the material that protects the ends of bones.

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The scientists say collagen from alligators could form replacement skin for burn victims. They say the collagen helps to heal wounds and stop bleeding. Doctors could also use it to treat some cancers, high blood pressure and the uncontrolled release of body wastes. The scientists say alligator collagen could also provide material for beauty products or foods.

Currently, collagen from cows and pigs is used in beauty products and for cooking. Mister Losso says scientists now are looking for other ways to get collagen because of concerns about mad cow disease. He and Mister Schexnayder say the protein also can be taken from sea creatures, including sharks.

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About two years ago, the Louisiana State University team started removing collagen from black drum and sheepshead fish. Masahiro Osawa of Japan designed the chemical process that enabled the removal. The team has asked the United States federal government for intellectual property protection for the process.

The team also compared alligator collagen and collagen from shark cartilage -- tissue that protects the ends of bones. The shark collagen is used in wound coverings, replacement for human skin or bone, and other material for medical operations. Mister Losso said the alligator and shark material are scientifically similar.

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In the United States, some alligators are killed for their meat. Their skin has considerable value for leather clothing, shoes and handbags. The state of Louisiana does not consider alligators endangered. State law permits limited harvesting of the animals.

The alligator parts that contain collagen are now usually thrown away. Louisiana alligators are responsible for more than four hundred fifty metric tons of unwanted parts each year. Destruction of this waste is costly.

Several years ago, Mister Schexnayder was asked to invent a purpose for this waste that would bring a profit. So he and Mister Losso went to work and came up with the idea of removing collagen from the dead animals. The United States Department of Commerce provided money for the experiments.

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Two weeks ago, we told you about a report critical of the medical value of homeopathic treatments. The report was published last month in The Lancet. It said that homeopathic treatments have the same effect as a placebo. A placebo looks like medicine but contains no active substance.

A German doctor, Samuel Hahnemann, developed homeopathic medicine in the seventeen nineties. He believed that some substances could cure diseases if they produced effects similar to those of the disease itself. He believed that these substances -- from plants, minerals or animals -- helped the body's own defense system to fight the sickness.

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The National Center for Homeopathy provides information about homeopathy to people in the United States. Recently, the group reported that several American scientists have rejected the Lancet report.

One of them is Joyce Frye of the University of Pennsylvania. She also is president of the American Institute of Homeopathy. This group represents the country's homeopaths.

Professor Frye says the study was strongly influenced by the opinions of the researchers. She said the researchers seemed to begin their work with a strong personal judgment, or bias.

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Professor Frye said the study cleared showed effects of homeopathic treatments, but the researchers found ways to avoid them. She also said the main findings depended on a comparison of only a few studies: eight tests of homeopathy and six tests of traditional medicine.

Iris Bell of the University of Arizona is another homeopath. She criticized the study for its methods of comparison. The researchers compared studies of homeopathic treatments with studies of medical drugs. Professor Bell says their methods are acceptable for studying traditional medicines, but not in comparing homeopathic treatments.

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VOICE ONE:

This program was written by George Grow, Cynthia Kirk and Jerilyn Watson. Our producer was Jill Moss. I'm Barbara Klein.

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And I'm Bob Doughty. Join us again next week at this time for another SCIENCE IN THE NEWS program in VOA Special English.