科学家完整绘制全套人类基因组

Scientists say they have finished mapping the full set of genetic information for human life.

The effort involved the first-ever sequencing of a complete human genome. A group of international researchers announced the result on March 31.

The researchers said the latest sequencing work filled in all remaining information needed for a full map of the human genome. The research was published in a series of studies in the publication Science. A first version of the research was published last year before it was examined by the scientific community.

In 2003, scientists released what was described at the time as a complete sequence of the human genome. But the international research team said the earlier effort did not include about eight percent of the genome. The past failure to complete the full map was linked to limitations in sequencing technology in use at the time.

Evan Eichler is a researcher at the University of Washington who took part in the latest effort. He was also part of a past research effort known as the Human Genome Project.

Eichler told The Associated Press that some of the genes that make us different as humans were contained in what he called the "dark matter of the genome." He said the earlier sequencing efforts missed those parts. "It took 20-plus years, but we finally got it done," Eichler said.

Many people, including Eichler's own students, thought the full sequence had already been completed. "I was teaching them, and they said, 'Wait a minute. Isn't this like the sixth time you guys have declared victory?'" Eichler said. He answered, "No, this time we really, really did it."

Karen Miga is a genomics researcher at the University of California-Santa Cruz. She helped lead the latest research. Miga told the AP that scientists hope the results will open the door to new medical discoveries in areas such as aging, the nervous system, cancer and heart disease.

The human genome is made up of about 3.1 billion DNA chemical base pairs, known by the letters A, T, G and C, the National Human Genome Research Institute explains. Each of these base pairs are contained in 23 pairs of chromosomes found in the nucleus of human cells.

Each chromosome contains hundreds to thousands of genes. The genes provide instructions for making proteins, the building blocks of life. An estimated 30,000 genes make up the human genome.

Until now, Miga said there were "large and persistent" elements missing from important areas of the human genome map. So Miga worked with Adam Phillippy, of the National Human Genome Research Institute, to organize the team of scientists to start over with a new genome. The group's goal was to sequence all of it.

The effort added new genetic information to the human genome and corrected past errors. It also identified long stretches of DNA known to play important parts in both evolution and disease.

Eichler, the University of Washington researcher, noted that some scientists used to think unknown areas of the genome contained "junk." But he said he never thought that way. "Some of us always believed there was gold in those hills," he told the AP.

That means he always believed they were valuable. Eichler said some of the unknown areas included many important genes.

I'm Bryan Lynn.

Reuters and The Associated Press reported on this story. Bryan Lynn adapted the reports for VOA Learning English.

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sequence – n. the order in which nucleotides (chemical substances) are combined to form DNA

genome – n. the complete set of genetic material of a human, animal, plant or other living thing

DNA – n. (deoxyribonucleic acid) a substance that carries genetic information in the cells of plants and animals

pair – n. two things of the same appearance and size that are intended to be used together

building block –n. an important part that is grouped together with many other similar things to form something larger

persistent – adj. doing something continually for a long time until a certain result is reached

evolution – n. a gradual process of change and development

junk – n. things that are considered to be of no use of value, or of low quality