New DNA map shows gene variations

Instead of showing single variations in human DNA that make people unique, the map looks at differences in duplications and deletions of large DNA segments known as copy number variants or CNVs, which can help explain why some people are susceptible to illnesses such as AIDS and others are not.

8220;We8217;re a patchwork of DNA sequences, gains and losses,8221; Charles Lee of the Brigham and Women8217;s Hospital and Harvard Medical School in Boston, Massachusetts, told a news conference.

Scientists identified about 3,000 genes with variations in the number of copies of specific DNA segments. The changes can affect gene activity, including susceptibility to diseases. The Human Genome Project mapped the billions of letters that make up the human genetic code. Scientists later refined the map by looking for single variations called SNPs or single nucleotide polymorphisms.

The scientists, whose findings are reported in the journals Nature, Nature Genetics and Genome Research, compiled the CNV map by comparing DNA from 270 healthy people in China, Japan, Nigeria and the United States.

The consortium identified 1,447 different CNVs that covered about 12 percent of the human genome. About 285 of them are associated with diseases, including schizophrenia, psoriasis, coronary heart disease and congenital cataracts.

8220;With these new tools, we are able to find previously undetectable deletions or duplications of the genome in a patient. The CNV map now allows us to identify which of these changes are unique to the disease,8221; said Dr Nigel Carter, of the Wellcome Trust Sanger Institute.

Genes important to the immune system and to brain development tend to have many CNVs, the researchers said. These are functions that have evolved rapidly in humans. 8220;I believe this paper will change forever the field of human genetics,8221; said James Lupski of the the Baylor College of Medicine in Houston, Texas.