Are genes our destiny? 'Hidden' code in DNA evolves more rapidly than genetic code, scientists discover

The study, published today in the journal Science, provides the first evidence that an organism's "epigenetic" code - an extra layer of biochemical instructions in DNA - can evolve more quickly than the genetic code and can strongly influence biological traits.

While the study was limited to a single plant species called Arabidopsis thaliana, the equivalent of the laboratory rat of the plant world, the findings hint that the traits of other organisms, including humans, might also be dramatically influenced by biological mechanisms that scientists are just beginning to understand.

"Our study shows that it's not all in the genes," said Joseph Ecker, a professor in Salk's Plant Molecular and Cellular Biology Laboratory, who led the research team. "We found that these plants have an epigenetic code that's more flexible and influential than we imagined. There is clearly a component of heritability that we don't fully understand. It's possible that we humans have a similarly active epigenetic mechanism that controls our biological characteristics and gets passed down to our children. "

With the advent of techniques for rapidly mapping the DNA of organisms, scientists have found that the genes stored in the four-letter DNA code don't always determine how an organism develops and responds to its environment. The more biologists map the genomes of various organisms (their entire genetic code), the more they are discovering discrepancies between what the genetic code dictates and how organisms actually look and function.

In fact, many of the major discoveries that led to these conclusions were based upon studies in plants. There are traits such as flower shape and fruit pigmentation in some plants that are under the control of this epigenetic code. Such traits, which defy the predictions of classical Mendelian genetics, are also found in mammals. In some strains of mice, for instance, a tendency for obesity can pass from generation to generation, but no difference between the genetic code of fat mice and thin mice explains this weight difference.

Scientists have even found that identical human twins exhibit different biological traits, despite their matching DNA sequences. They have theorized that such unexplained disparities could be the work of epigenetic variation.

"Since none of these patterns of variation and inheritance match what the genetic sequence says should happen, there is a clearly a component of the 'genetic' heritability that is missing," Ecker said.

Full Article: [link to www.physorg.com]

Last Edited by Heretic™ on 09/17/2011 06:54 AM