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The First Sequenced Chromosome
| Article
# : |
20083 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
12 / 1992 |
2,676 Words |
| Author
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Stephen G. Olivier
Stephen G. Oliver is a molecular biologist at the Manchester
Biotechnology Centre of the University of Manchester
Institute for Science and Technology in England. He was the
DNA coordinator of the international project that completed
the decoding of yeast's chromosome III last spring. |
The eighteenth and nineteenth centuries saw the relentless accumulation of facts about the living world. Organisms were collected and named, and biologists attempted to arrange the rich diversity of nature into some logical order. It was then that they realized that their newfound depth of knowledge about living things revealed the depths of their ignorance. This realization provoked the development of evolutionary theory, finally articulated with startling clarity and insight by Charles Darwin.
Biologists today are in a similar position. Though not roaming the world with nets and specimen jars collecting organisms, they are busily engaged in laboratories collecting genes--the molecular instructions for the operation of life, contained in the DNA coiled within the chromosomes in every cell. Until recently genes were identified on the basis of their function, by recognizing changes in the activities of organisms as a result of mutations. In this traditional approach to genetics, gene identification was limited by the available fund of knowledge regarding the biology of the organism under study. It was impossible to know the unknown.
Modern techniques of DNA sequencing have changed all that [see box]. Molecular geneticists now have the means to directly identify an organism's entire genome (all of the genes in that organism) by determining the order in which the four "letters" of the genetic code--the nucleotides adenine, thymine, guanosine, and cytosine--are arranged in cryptic "words" in the DNA of its chromosomes. The ultimate aim is to determine the complete DNA sequence of all the chromosomes that make up the human genome. It is calculated that the human genome contains some three billion such nucleotide letters. (In the jargon of molecular biology, the human genome size is 3,000 Megabases, or 3,000 Mb.) This immense task will require significant improvements in the current sequencing technology as well as a worldwide collaboration among scientists. En route to this final goal, there will be a number of milestones--smaller achievements that while facilitating the interpretation of the human genome will have great scientific importance in their own right. These milestones will provide both a dictionary and a map to allow us to find our way through the complexity of our own chromosomes [see "How DNA Is Sequenced"]. This article tells the story of the first of these: the complete determination of the DNA sequence of an entire chromosome--chromosome III of the brewing and baking yeast, Saccharomyces cerevisiae.
Why yeast?
...
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