Variety-Sized Pups

Clifford the SMALL Red Dog??? That can’t be right!

This is Sandra Tsing Loh with the Loh Down on Science.

“My dog’s bigger than your dog…” But wait – how can itty-bitty chihuahuas and HUMONGOUS Saint Bernards BOTH be dogs? Hint – it’s not the Ken-L-Ration! 

Jocelyn Plassais from the National Human Genome Research Institute and colleagues wondered. They studied the DNA of canines looking for size-linked differences.

Genes have different forms, or alleles, that determine characteristics. And guess what — the researchers found two different variants for the IGF1 gene that affect size in modern dogs! Dogs with matching BIG-sized alleles weighed about fifty pounds or more. Those with matching SMALL-sized alleles? Less than thirty! One of EACH allele meant medium-sized pooches. Ancient canines had these characteristics too!

These alleles may explain how a teeny Pomeranian and huge Great Dane are the same species! This isn’t the ONLY genetic factor that affects how big a dog gets. But this is a step towards finding the origins of differing dog sizes!

I guess it’s not im-PAW-sible that Clifford had smaller ancestors after all!

Reference: Plassais, J., vonHoldt, B. M., Parker, H. G., Carmagnini, A., Dubos, N., Papa, I., Bevant, K., Derrien, T., Hennelly, L. M., Whitaker, D. T., Harris, A. C., Hogan, A. N., Huson, H. J., Zaibert, V. F., Linderholm, A., Haile, J., Fest, T., Habib, B., Sacks, B. N., Benecke, N., … Ostrander, E. A. (2022). Natural and human-driven selection of a single non-coding body size variant in ancient and modern canids. Current biology : CB, 32(4), 889–897.e9.