Small differences between individuals at the DNA level can give rise to dramatic differences in the way genes produce proteins, say McGill University researchers.
Dr. Jacek Majewski, who led a study as part of the Genome Regulators in Disease (GRID) Project funded by Genome Canada and Genome Quebec, says that their work provides an insight into how a relatively small number of differences within DNA protein coding sequences could be responsible for the enormous variety of phenotypic differences between individuals.
Previous studies had revealed that individual differences reside in simple and relatively small variations in the DNA sequence called single nucleotide polymorphisms (SNPs), which exist primarily in the "junk code" of the DNA that was not earlier known to have any profound genetic effect.
"There are many SNPs," Nature Genetics quoted Dr. Majewski as saying.
"If you add them all together, you'd expect that two individuals would differ at more than a million of those positions. So we have a million or more small differences that distinguish you and me, and yet it would be very hard to explain all the phenotypic differences in the way we look, grow, and behave just by the handful of these protein coding differences," he added.
His team has shown that the SNPs genetically control the natural processing of messenger RNA (mRNA) through a process called splicing.
Dr. Majewski says that the SNPs cause changes in splicing in certain individuals, and result in the production of drastically altered forms of the protein.
Such out-of-proportion consequences may lead to the development of genetic diseases like cystic fibrosis and Type 1 diabetes, he adds.
The study was originally initiated by Dr. Tom Hudson, former director of the McGill University and Genome Quebec Innovation Centre.
It drew upon the data collected by the vast HapMap Project, a global comparative map of the human genome, which Hudson and his colleagues were instrumental in completing.