A biologist with the Commerce Department's National Institute of Standards and Technology (NIST) led the research team, which reported its findings in the March 10 online edition of Molecular Biology and Evolution. The results are based on a systematic, statistically rigorous analysis of publicly available genetic data carried out with bioinformatics software developed at CARB.
In humans, there is so much apparent "junk" DNA (sections of the genome with no known function) that it takes up more space than the functional parts. Much of this junk consists of "introns," which appear as interruptions plopped down in the middle of genes. Discovered in the 1970s, introns mystify scientists but are readily accounted for by cells: when the cellular machinery transcribes a gene in preparation for making a protein, introns are simply spliced out of the transcript.
Research from the CARB group appears to resolve a debate over the "early versus late" timing of the appearance of introns. Since introns were discovered in 1978, scientists have debated whether genes were born split (the "introns-early" view), or whether they became split after eukaryotic cells (the ones that gave rise to animals and their relatives) diverged from bacteria roughly 2 billion years ago (the "introns-late" view). Bacterial genomes lack introns. Although the study did not attempt to propose a function for introns, or determine whether they are beneficial or harmful, the results appear to rule out the "introns-early" view.
The CARB analysis shows that the probability
Contact: Laura Ost
National Institute of Standards and Technology (NIST)