Canine muzzle points to speedy evolution

New research on evolution of canine shapes

source: Bob Holmes
New Scientist vol 184 no 2478, December 18 2004 p10

Variations in repeating DNA sequences can account for variations in head shapes across dog breeds. John Fondon and Harold Garner from the Southwestern Medical Center, University of Texas, looked at 92 dog breeds, sequencing 37 repeated regions coming from 17 genes affecting development. Runx-2 is a gene which affects head shape. Breeds with short noses, like pugs, were found to have repeats inside one particular gene giving codes for a high number of alanine amino acid repeats, and a low number of glutamine amino acid repeats. The reverse was true for greyhounds and other long-nosed breeds. The protein product of the genes affects how bone-producing cells differentiate. This helps to explain the great variation in canine shapes and sizes which have arisen in a few thousand years.