Humanness as a numbers game

Font Size

Print

Feedback

Email

Discuss

: Human beings may not think of themselves as the centre of all creation any longer, but they are regarded as unique, at least among their close primate cousins. The “why” may just have begun to fall in place, unveiling a jigsaw puzzle that has interested researchers for long but with few tangible clues to advance a plausible explanation.

From time to time, the role played by chromosomal variations in the genome has helped explain certain phenomena, such as Down’s syndrome, a genetic disorder caused by the additional presence of the entire or part of the 21st chromosome that is manifested by major and minor variations in body structure resulting in impairment of cognitive ability and physical growth as well as facial appearance.

On the other extreme of chromosomal abnormality, non-disjunction of a chromosome results when homologous chromosome pairs do not separate during meiosis. These variants, resulting in deletion, duplication, translocation or inversion, are all examples of chromosomal abnormalities. The Turner syndrome (females missing one X chromosome) is another example that manifests itself in several ways, including amenorrhoea, sterility, obesity and so on. Thus, the copy number of genes has long been associated with certain physical and physiological irregularities leading to impairments.

Recent advances in molecular studies and comparative genomic hybridisation, that came into the limelight for their fascinating applications in oncology, have begun to shed light on yet another facet of human behaviour that has eluded characterisation until now.

James Sikela of the University of Colorado, Denver and Health Sciences Center in Aurora, and his colleagues have come out with a novel hypothesis on the role of gene copy number variation in humans and our closest relatives. In a recent paper published in Genome Research, comparisons between DNA from more than 24,000 known human genes, with DNA from baboons, bonobos, chimpanzees, gibbons, gorillas, lemurs, macaques, marmosets and orangutans elicited a bewildering pattern. Quite an exhaustive and comprehensive project of research, no one till date quite seems to have probed such vast data among such a diverse group of closely related species.