Geenit yksilökohtaisia

The results show that most genes can occur in many different forms within a population: On average, about 250 different forms of each gene exist. The researchers found around four million different gene forms just in the 400 or so genomes they analysed. This figure is certain to increase as more human genomes are examined. More than 85 percent of all genes have no predominant form which occurs in more than half of all individuals. This enormous diversity means that over half of all genes in an individual, around 9,000 of 17,500, occur uniquely in that one person - and are therefore individual in the truest sense of the word.

The gene, as we imagined it, exists only in exceptional cases. "We need to fundamentally rethink the view of genes that every schoolchild has learned since Gregor Mendel's time. Moreover, the conventional view of individual mutations is no longer adequate. Instead, we have to consider the two gene forms and their combination of variants," Hoehe explains. When analysing genomes, scientists should therefore examine each parental gene form separately, as well as the effects of both forms as a pair.

According to the researchers, mutations of genes are not randomly distributed between the parental chromosomes. They found that 60 percent of mutations affect the same chromosome set and 40 percent both sets. Scientists refer to these as cis and trans mutations, respectively. Evidently, an organism must have more cis mutations, where the second gene form remains intact. "It's amazing how precisely the 60:40 ratio is maintained. It occurs in the genome of every individual – almost like a magic formula," says Hoehe. The 60:40 distribution ratio appears to be essential for survival. "This formula may help us to understand how gene variability occurs and how it affects gene function."

http://medicalxpress.com/news/2014-11-duality-human-genome.html