A new technology has shown that a single parent can pass on more than one copy of a gene.india Updated: Nov 27, 2006 00:57 IST
The latest revelations of the human genome are really a celebration of diversity. Turning prevalent notions of what constitutes ‘normal’ and what ‘abnormal’ on its head, the new discoveries show that the previously held belief that humans are more than 99 per cent genetically identical is wrong. Researchers studied the genomes of 270 volunteers from across the world to establish that while people inherit one chromosome from either parent, it is not necessary that they inherit one copy of a given gene from the mother and one from the father.
Genes are the units of hereditary characteristics. Humans carry about 30,000 genes. It was thought that people carry only two copies of a gene, one from either parent. But now, new technology has shown that a single parent can pass on more than one copy of a gene. In fact, a person can have even 10 copies of a gene — or none at all. This implies that natural variation in the human genome is much larger than believed and, thus, a closer look is required before assigning a variation as ‘abnormal’, or understanding the import of a particular gene’s function. For instance, a shorter chromosome is traditionally believed to imply some mental retardation or developmental delay. But the new gene map showed that, in several cases, shorter chromosomes existed in ‘normal’ people. This means that diagnostics that pointed to foetal abnormality on this count may have been misplaced. While this kind of understanding offered by scientists is still in the realm of speculation, the new Haplotype Map is bound to be an atlas of intrigue and secrets. The medical implications of this ‘discovery’ are obvious.
The very fact that there may well exist no ‘standard minimum’ that defines ‘normalcy’ is in itself a signal for a more cautious approach to extrapolating on genetic function and ‘profiling’ genes. The work further highlights how DNA makes each human being unique. It provides the landscape to study the genetics of disease — including Alzheimer’s, cancer and Aids. Finally, it also shows that the trick to using the genome map successfully lies in interpretation and coming to correct conclusions. In other words, by not holding on to stereotypes.