Predictive medicine

Genome mapping has huge benefits but downsides as well

Bio-sciences are driven by clever deployment of vast computational power. Breakthroughs involve bewildering combinatorial mathematics as scientists ponder the consequences of DNA strands being arranged in multitudes of different orders. As the associated effects of DNA combinations become better-known, understanding about genetic predispositions increases. Eventually, it will be possible to take a drop of blood from an infant and predict the baby will grow to say, a height of 1.8 metres, be capable of running 100 metres in 10 seconds, have a tendency to put on weight and some susceptibility to diabetes. Genome sequencing is a new technique. It has been demonstrated on a few individuals in the US, South Korea, China, the UK and Canada. India has just joined this club. A team led by Rajesh Gokhale of the Institute of Genomics and Integrative Biology (IGIB), (a division of the Council of Scientific and Industrial Research), has decoded the genome sequence of a 52-year-old man from Jharkhand. Though the subject is currently healthy, the team could state with confidence that he is susceptible to bipolar disorder, collateral cancers, ulcers and coronary disease. The IGIB is now scaling up genome sequencing to study 10 individuals at an estimated cost of about Rs 1.5 lakh per person. Eventually, broader predictions about the genetic predispositions of ethnic groups will become possible.

 

The consequences for preventive medicine are incalculable but huge. Once individuals can be sequenced cheaply, at will, they can be warded against diseases, allergies and conditions to which they are vulnerable. What is more, predictions can be made about their children, even before such children are born. By analogy, a confluence between cheap computing power and detailed satellite imaging has completely altered perspectives on geographical location. A GPS-equipped vehicle automatically maps routes between random addresses. A real estate investor can check out properties sitting at her desk. Similar effects will arise in medicine as granularity of information about genomes increases. A genome is the sum total of genetic instructions about a living being. It comprises the chromosomes, which, in turn, are made up of genes that are built from strands of DNA. The genome is unique to the individual (except with identical twins). Once exact DNA sequences for an individual are known, startlingly exact, long-term predictions are possible. Vulnerability to many diseases, including diabetes and cancer for example, is associated with specific DNA strands (markers) in specific chromosomes. Earlier maps had found such markers but sequencing, which locates the position of every DNA strand, is orders of magnitude more exact. It is the difference between knowing where Delhi is, and being able to locate say, “4, Bahadur Shah Zafar Marg (the BS address)” in a second. By sequencing large populations, understanding about diseases and their prevention will grow exponentially. It would be possible to personalise medicine to exactly suit the needs of individuals.

There may be a dark side as amniocentesis can identify crucial foetal abnormalities but also enable female infanticide. Genome sequencing is a dream for racists. In the Indian context, it could reinforce caste-based prejudices. On the other hand, the benefits are obvious. In the long run, scientists estimate that breakthroughs from genome sequencing could add 20-30 years to average lifespans. Technology, as always, remains a tool. It is up to society to use it wisely.