SCI/TECH/Experimental research
“Variation in DNA-minor”

Scientists at The Hospital for Sick Children (Sick Kids), Brigham and Women's Hospital (BWH) and Harvard Medical School (HMS) have some unexpected news: they claim that significant differences exist in the overall content of DNA and genes contained in individual genomes.

Their findings will be published in the September 2004 issue of the scientific journal, “Nature Genetics”.

"Using new genome scanning technologies, we serendipitously found stretches of DNA, sometimes hundreds of thousands of chemical bases (nucleotides) long, that were present or absent in the genomes of healthy individuals. These large-scale copy variations, or LCVs, frequently overlap with genes…” said Dr. Stephen Scherer, co-principal investigator of the study.

"At first we were astonished and didn't believe our results because for years we had been taught that most variation in DNA was limited to very small changes. Then we heard the Harvard group was making similar observations and ultimately we combined our data and came to the same conclusion," he added.

Early information from the Human Genome Project indicated that the DNA in the genome of any two individuals is 99.9 per cent identical.

The new data from the Sick Kids and Harvard groups revealed 255 regions of the genome where large chunks of DNA are present in different copy numbers between individuals.

"For example,” says co-principal investigator Dr. Charles Lee, “the most common LCV involves amylase genes. Our study shows that some people may have 10 copies of this gene while others may have as much as 24 copies of this same gene.”

Over 50 per cent of these alterations lead to changes in gene numbers and at least 14 regions overlapped with known sites associated with human disease.

"Because these newly discovered variants exist in the genomes of healthy individuals, their presence could lead to subtle differences affecting physical or behavioral traits,” says Lee.

Information on identified LCVs will be added to the publicly-accessible Genome Variation Database.

Get more info: University of Toronto: (416) 813-5046

Find more science news in the August 2004 issue of "Arte Six".