Scientists have built a detailed map of human genetic variation, using resources from an early 1,000 Genomes project. The research has found new clues about human disease, including why some people are more severely affected by disease than others.

Dr. Evan Eichler of the University of Washington in Seattle and colleagues used findings from the pilot phase of the project to identify subtle differences among people in areas of the genome where DNA sequences are often repeated many times.

"I believe this is where we will make huge inroads in understanding the genetic basis of human disease," Eichler said.

His findings were released in the journal Science to coincide with publication in Nature of the first data from the 1000 Genomes Project. Researchers expect that the data would offer a new set of tools to help understand the genetic causes of disease.

DNA sequences, known as copy number variation, have traditionally been difficult to compare, Wichler noted. But, they may be able to explain why some people are more severely affected by disease than others.

In a press briefing here, Eicheler also said that duplications of segments of the genome appear to have led to many of the qualities that distinguish human beings from other primate species. And they also may be linked with diseases like schizophrenia and autism, he said.

Researchers have uses advanced machinery that can help sequence genetic information, to speeden the process. The machines are developed by companies like Illumina and Roche.

"Already, just in the pilot phase, we've identified over 15 million genetic differences by looking at 179 people. Over half of those differences haven't been seen before," said Dr. Richard Durbin, group leader of the Wellcome Trust Sanger Institute and co-chair of the 1000 Genomes Project.

"This is the largest catalog of its kind, and having it in the public domain will help maximize the efficiency of human genetics research," Durbin told a news briefing.

Researchers noted that the pilot includes data from more than 800 people, highlighting around 16 million variations in the genetic code that were previously unknown.They have identified 95 per cent of the genetic variants in any individual, which will help as teams try to assess the genetic causes of both rare and common genetic diseases.

Researchers also found that each individual carries a huge number of potentially dangerous genetic mutations, with maybe 250 to 300 genes that have defective copies.The new map might allow researchers to look at the effects of recent evolution on the human genome.