Jacek Majewski and Tony Kwan of McGill University said their findings, in part, explain how a relatively small number of differences within DNA protein coding sequences can cause the enormous variety of phenotypic differences between individuals.

Majewski noted there are numerous variations in the DNA sequence called single nucleotide polymorphisms, or SNPs, that exist primarily in "junk code" -- DNA not known to have any profound genetic effect.

"There are many SNPs," said Majewski. "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."

Majewski and colleagues demonstrated SNPs can produce drastically altered forms of protein, possible leading to the development of genetic diseases such as cystic fibrosis and Type 1 diabetes.

The complex research is reported in the journal Nature Genetics.

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