Whoever said people were much the same was wrong!

Nov 22 2006

An international research team have come up with a new genetic map which could demand a fundamental shift in how we think genes work.

The research has already had an impact on the diagnosing of some genetic diseases.

Hundreds of unusual mutations have been found in a newly updated map of the human genome, by Stephen Scherer, a geneticist at the University of Toronto and the Hospital for Sick Children, and his colleagues.

In order to draw the map DNA was analysed from 270 individuals, from four populations, with ancestry in Europe, Africa or Asia.

The results show that people are far more genetically variable than first thought and the researchers say the new map shows genes don't always line up as expected and there can be mismatches, or chunks with missing or extra DNA.

Scherer says the discovery really changes things, as it shows that people are far more genetically variable than first thought.

Scherer's team mapped the number of duplicated or deleted genes, which they call copy number variations (CNVs).

Mismatched genes and rogue chunks of DNA can cause profound and mysterious health problems that could explain some forms of autism, heart defects and Alzheimer's disease, say the researchers.

In general genes occur in two copies, one inherited from each parent and the researchers found around 2,900 genes, or more than 10 per cent of the human genome, had variations in the number of copies of specific DNA segments.

Until now, research on genetic diseases has focused on small changes called single nucleotide polymorphisms, or SNPs and the discovery may mean that some diseases are instead caused by differences in the number of copies.

Recent research has suggested that could be true for some types of kidney disease, Parkinson's disease, and Alzheimer's as well as susceptibility to AIDS.

The group found nearly 16 percent of known disease-related genes in the CNVs, including genes involved in rare genetic disorders such as DiGeorge, Angelman, Williams-Beuren, and Prader-Willi syndromes, as well as those linked with schizophrenia, cataracts, spinal muscular atrophy and atherosclerosis.

Study co-author Martin Somerville, a professor of medical genetics at the University of Alberta, discovered a connection between pinched blood vessels and missing DNA.

He found six cases where a missing strand of DNA corresponds with an identical heart condition, which he says was rather like 'a kink in a hose' of that main vessel.

The research is published in the current issue of the journal Nature.