A DOG’S nose can tell us a lot about evolution. Whether a breed has the scrunched-up nose of a boxer or the long snout of a greyhound depends on whether it inherits certain small stretches of repeating DNA sequences. The surprise finding that such easily achieved genetic changes can produce obvious new traits hints that this may be one way in which rapid evolution takes place.
Within the coding regions of genes, a particular three-letter sequence of DNA bases can be repeated many times. These repeats direct the production of long strings of the same amino acid within a protein.…
