U.S. study shows functional human genome less than 25 pct

HOUSTON, July 14 (Xinhua) -- A biologist at the University of Houston has calculated that at least 75 percent of the genome is junk DNA, according to a university report released on Friday.

Evolutionary biologist Dan Graur has published new calculations, indicating the functional portion of the human genome probably falls between 10 percent and 15 percent, with an upper limit of 25 percent. The rest is so-called junk DNA, or useless but harmless DNA.

The research result is in stark contrast to suggestions by scientists with the Encyclopedia of DNA Elements (ENCODE) project. In 2012, ENCODE announced that 80 percent of the genome had a biochemical function.

The ENCODE consortium is an international collaboration of research groups funded by the National Human Genome Research Institute (NHGRI). Its goal is to build a comprehensive parts list of functional elements in the human genome, including elements that act at the protein and RNA levels, and regulatory elements that control cells and circumstances in which a gene is active.

The calculations took a deceptively simple approach to determining how much of the genome is functional, using the deleterious mutation rate - that is, the rate at which harmful mutations occur - and the replacement fertility rate.

If 80 percent of the human genome to be functional, unrealistically high birth rates would be required to sustain the population even if the deleterious mutation rate were at the low end of estimates, Graur found.

Graur said this new study may help refocus the science of human genomics.