In recent years, the genetic mechanisms by which humans have generated massive phenotypic diversity in dogs have started to be uncovered. We now know, for example, much about the genetics of pigmentation in dogs, and a major gene controlling body size. This week, another phenotype–the short, stubby legs of some dog breeds (see right)–has been revealed to have a simple, but interesting genetic basis.
The authors mapped the short leg phenotype to a small region on chromosome 18; further analysis revealed that the probable causal mutation is the insertion of a transcriptionally-active processed (ie. intronless) retrotransposed copy of the FGF4 gene. How this change leads to the phenotype itself is unknown, but understanding the mechanism will likely lead to some interesting biology.