Genetic map that could unlock secrets of human life

Genetic map that could unlock secrets of human life

27.10.05 1.00pm
By Steve Connor

The first genetic "map" of human diversity is published today by scientists who describe it as a landmark achievement that will revolutionise medicine.

More than 200 researchers from six countries have spent three years and more than £80m deconstructing the human genome to discover the precise genetic differences between people.

Whereas the human genome - the basic genetic blueprint - showed that everyone shares 99.9 per cent of their genes, it is the 0.1 per cent difference that can hold the clues to illnesses such as asthma, diabetes, dementia, heart disease and cancer.

Scientists have completed the first phase of an ambitious project to tease apart these minute differences to begin to explain why some people develop serious diseases while others with a similar lifestyle remain healthy.

The map of human diversity could also be used to identify patients who respond better to certain drugs as well as explaining the evolutionary origins of humankind by shedding light on the ancient migrations of our ancestors from Africa.

"This represents a milestone for medical research," said David Altshuler of Harvard University, one of the leaders of the team to draw up the genetic map, published in the journal Nature.

Dr Altshuler said that the map provides a powerful new tool for exploring the root causes of the many common diseases that have a genetic as well as lifestyle component.

"Such understanding is required for researchers to develop new and much-needed approaches to prevent, diagnose and treat diseases such as diabetes, bipolar disorder, cancer and many others," he said.

The scientists built up the map of genetic diversity from a detailed analysis of the DNA from 269 volunteers drawn from four different ethnic groups - the Yoruba tribe from Nigeria, residents of Tokyo, the Han Chinese from Beijing and European Americans from Utah.

By painstakingly comparing the smallest possible mutations - called single nucleotide polymorphisms - in each of the volunteer's DNA, the scientists produced the first comprehensive catalogue of human genetic variation.

Panos Deloukas, a senior investigator at the Wellcome Trust Sanger Institute in Cambridge, said that a map of such differences will ultimately prove invaluable in understanding the many life-threatening diseases affecting people today.

"Humans are genetically 99.9 per cent identical.

It is the tiny percentage that is different that holds the key to why some of us are more susceptible to common diseases such as diabetes and hypertension or respond differently to treatment with certain drugs," Dr Deloukas said.

The new genetic map is based on relatively large fragments of DNA - called haplotypes - that contain a unique battery of single mutations which tend to be inherited together as a block.
Scientists have called the study "HapMap" because it is based on these human haplotypes.

More than a million single mutations have so far been mapped to their respective haplotypes.

The researchers estimated that the study will increase by 20-fold the speed at which it is possible to search for the genes responsible for disease.

"This report describes a remarkable step in our journey to understand human biology and disease," said Professor Peter Donnelly of the University of Oxford, another senior member of the research team.

All the information resulting from the study - which was funded jointly by governments and private industry - is available on the internet.

Preliminary data has already been used by researchers to identify the genetic mutations behind age-related macular degeneration, a condition that causes blindness in older people.

"The HapMap is a remarkable resource that will accelerate the search for genes involved in common ailments, such as heart disease and obesity," said Mark Wolport, director of the Wellcome Trust, which helped to fund the project.

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