O conceito de gene está obsoleto.

sábado, maio 03, 2014

Your Genes Are Obsolete

BY MICHAEL WHITE • May 02, 2014 • 8:00 AM

(Photo: Leigh Prather/Shutterstock

Today, DNA is central to modern biology, but scarcely a century ago biologists were debating whether or not genes actually existed. In his 1909 textbook on heredity, Danish botanist Wilhelm Johannsen coined the term gene to refer to that hereditary “something” that influences the traits of an organism, but without making a commitment to any hypothesis about what that “something” was. Just over a decade later, a prominent biologist could still note that some people viewed genes as “a convenient fiction or algebraic symbolism.”

As the century progressed, biologists came to see genes as real physical objects. They discovered that genes have a definite size, that they are linearly arrayed on chromosomes, that individual genes are responsible for specific chemical events in the cell, and that they are made of DNA and written in the language of the Genetic Code. By the time the Human Genome Project was initiated in 1988, researchers knew that a gene was a segment of DNA with a clear beginning and end and that it acted by directing the production of a particular enzyme or other molecule that did a specific job in the cell. As real things, genes are countable, and in 1999 biologists estimated that humans had “80,000 or so” of them.

Yet, when the dust from the Human Genome Project cleared, we didn’t havenearly as many genes as we thought. By the latest count, we have 20,805 conventional genes that encode enzymes and other proteins. Our inflated gene count, though, wasn’t the only casualty of the Human Genome Project. The very idea of a gene as a well-defined segment of DNA with a clear functional role has also taken a hit, and as a result, our understanding of our relationship with our genes is changing.

One major challenge to the concept of a gene is the growing evidence that many genes are shapeshifters. Instead of a well-defined segment of DNA that encodes a single protein with a clear function, we should view a gene as “a polyfunctional entity that assumes different forms under different cellular states,” according to University of Washington biologist John Stamatoyannopoulos. While researchers have long known that genes are made up of discrete subunits called “exons,” they hadn’t realized until recently the degree to which exons are assembled—like Legos—into sometimes thousands of different combinations. With new technologies, biologists are cataloging these various combinations, but in most cases they don’t know whether those combinations all serve the same function, different functions, or no function at all.

Read more here/Leia mais aqui. PS MAG