5 Apr 2012


At one time, determining the sequence of nucleotides in a particular type of DNA was difficult and time-consuming. In the 1960s, it took seven years to determine the sequence of a DNA molecule with only 77 nucleotides. Now, like many other tasks, the analysis of DNA is automated. Laboratory equipment analyzes DNA quickly, and computers tabulate the results. Because of these technological advances, in the late 1980s molecular biologists began to plan for what they considered the most important biology investigation of all time: determining the entire nucleotide sequence of human DNA. In 1992, a worldwide effort—the Human Genome Project—began to analyze the three billion base pairs of human DNA. If printed on paper, the linear sequence of DNA contained in each of our cells would require 2000 books the size of this one. Molecular biologists all over the world are working together on this project, and they expect to finish before the year 2005.

In 1998, a well-known geneticist, along with a highly respected research company that makes machines to analyze DNA, announced that they planned to map the human genome faster and for less money than the government-sponsored Human Genome Project. They claimed that for only $200 million they would be done in just three years. The public may have been concerned that one private company could control so

Death-Row Inmate Cleared by DNA Evidence

Every time a prisoner awaiting a death sentence is proven innocent by DNA evidence and released, it makes the news. And it should. Nothing demonstrates the power of DNA technology better. Ray Krone owes his freedom, and probably his life, to this technology. In 2002, he was released from an Arizona prison after serving 10 years. During that time, Mr. Krone, who had served in the U.S. Air Force and worked as a letter carrier with no criminal record, was tried twice for the sexual assault and stabbing murder of a bartender in 1991. Mr. Krone was in the bar where the victim worked the night of the murder. The only evidence used to convict him was the similarity between the pattern of tooth marks on the victim, where she had been bitten, and Mr. Krone’s teeth.
The first trial sentenced Mr. Krone to death, the second trial to a life sentence. Finally, after 10 years, DNA testing was done on saliva from bite marks found on the victim’s clothing. Not only did the DNA not match that of Mr. Krone, but it did match that of a person serving time in another Arizona prison for an unrelated sex crime. The odds were 1.3 quadrillion (1,300,000,000,000,000) to 1 that it was this other man’s DNA on the victim and not that of Mr. Krone or anyone else. A judge ordered the immediate release of Ray Krone when the DNA test results were announced.

much important information. However, most scientists agreed that the sooner the complete human genome was decoded, the sooner more research could be conducted to understand what it all means. By 2001, the first working draft sequence of the entire human genome was published.

Scientists agree that the Human Genome Project, described by some people as the effort to read the “book of humankind,” is just the beginning of human genetic research. Only through this effort will we be able to understand ourselves on the molecular level, the most basic level of all. Indeed, scientists aim to someday understand all life-forms on this level. In 2002, six more model organisms were chosen to have their entire genetic codes spelled out. These six are the chimpanzee, the chicken, the honeybee, the sea urchin, a yeastlike protozoan, and a family of fungi.

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