"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 and could explain why people are different," said Dr. Stephen Scherer, co-principal investigator of the study, a Sick Kids senior scientist, and an associate professor in the Department of Molecular and Medical Genetics at the University of Toronto.
"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," added Dr. Scherer.
Early information from the Human Genome Project indicated that the DNA in the genome of any two individuals is 99.9 per cent identical with the 0.1 per cent variation arising primarily from some three million single nucleotide changes scattered amongst the chromosomes. The new data from the Sick Kids and Harvard groups revealed 255 regions (comprising more than 0.1 per cent) of the genome where large chunks of DNA are present in different copy numbers between individuals. Over 50 per cent of these alterations lead to changes in gene numbers and at least 14 regions overlapped with known sites ass
Contact: Laura Greer
University of Toronto