Editorial: What genome sequencing reveals

Published in The Hindu on March 23, 2010

How rich human genetic diversity is has been revealed by the fully sequenced genomes of an indigenous southern African hunter-gatherer belonging to the Khoisan or Bushmen community, and a Bantu individual. The Bantu individual is none other than liberation hero and Nobel Laureate Desmond Tutu. This is the first time that genomes of minority populations in Africa have been sequenced. The study, published recently in Nature, shows that southern Africans have about 1.3 million novel DNA differences compared with the genomes of West Africans, Asians, and Europeans. In addition to the genetic differences, partial genome sequencing of three more Bushmen revealed that they have 13,146 amino acid variants. Such is the genetic variation that two of the Bushmen studied, who may at times be within walking distance of each other, are more different than, for instance, a European and an Asian. Previous studies indicated an extraordinarily high level of genetic variation among indigenous populations in Africa. This was only to be expected as humans had lived in southern Africa much longer than in any other part of the world, and therefore had greater chances of accumulating genetic differences. A comparison of the Bushmen’s single nucleotide polymorphisms (SNP) with those of the chimpanzee’s reveals that very few of the differences seen in their genome are ancestral.

The latest study has important implications for medical research. It will help in identifying diseases caused by genetic variations, and in understanding how genetic variations influence the effectiveness of drugs — a field of medical research called pharmogenomics. With no genomic data of southern Africans available, all pharmogenomic research and genetic disease susceptibility studies carried out so far have mostly used European genome sequences. As the sequenced data of all the five individuals are freely available, drug companies will be better equipped to produce drugs for these populations, and understand why Bushmen are particularly susceptible to TB. The results have inspired a more detailed investigation of the neglected people of Africa. The same team of researchers has begun to study different ethnic groups in Africa; the recruitment of volunteers has begun; and specific information from the present study has been incorporated for quicker and detailed investigation.