Brewing up a double genome.Beer lovers owe a debt of gratitude to Saccharomyces Saccharomyces: see yeast. cerevisiae, the yeast commonly used to generate the alcohol in beer. Now, a new genetic analysis suggests that the organism's alcohol-making ability developed as a result of an accidental duplication of the entire yeast genome millions of years ago. In the June 12 Nature, Kenneth H. Wolfe and Denis Denis, king of Portugal: see Diniz. C. Shields of Trinity College Trinity College, Ireland: see Dublin, Univ. of. Trinity College Private liberal arts college in Hartford, Conn., founded in 1823. It is historically affiliated with the Episcopal church, though its curriculum is nonsectarian. in Dublin contend that two yeast cells once merged to create a cell that had four sets of chromosomes. This ancestor ANCESTOR, descents. One who has preceded another in a direct line of descent; an ascendant. In the common law, the word is understood as well of the immediate parents, as, of these that are higher; as may appear by the statute 25 Ed. III. De natis ultra mare, and so in the statute of 6 R. of S. cerevisiae quickly eliminated most, though not all, of the extra genes and settled back to two sets of chromosomes. "What we see now is the remains of an event that happened a long time ago," says Wolfe. The researchers base their conclusion on finding more than 370 instances in which S. cerevisiae has two almost identical copies of a gene on a single chromosome. The orientation and placement of these gene pairs suggests that they did not result from the copying of individual genes but from the duplication of an entire genome, say Wolfe and Shields. The extra genes that S. cerevisiae did hold onto may have evolved to endow en·dow tr.v. en·dowed, en·dow·ing, en·dows 1. To provide with property, income, or a source of income. 2. a. the yeast with new abilities. Several of the gene pairs, for example, contain a gene activated in the presence of oxygen and one activated when no oxygen is present. This may help explain why, unlike its close relatives in the yeast world, S. cerevisiae prefers fermentation--which uses sugars but no oxygen to generate energy and alcohol--to forms of respiration respiration, process by which an organism exchanges gases with its environment. The term now refers to the overall process by which oxygen is abstracted from air and is transported to the cells for the oxidation of organic molecules while carbon dioxide (CO that use oxygen, says Wolfe. |
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