Waddington Experiment

Conrad Hal Waddington performed several experiments to provide evidence in support of genetic assimilation, a Darwinian concept to explain inheritance of acquired characters. The one described by Jonathan M W Slack is illustrated here [1].

Fruit flies Drosophila have a small vein crossing the middle their wings. This crossvein can be made to disappear in some individuals by brief hight temperature exposure during pupation. If individuals that show the crossveinless phenotype are selected and the heat treatment and selection steps repeated several times, we end up with fruit flies that eventually show the crossveinless phenotype without any heat treatment.

The crossing vein is symbolized by a red line on the wings of the fly left. If their pupae are exposed to heat a generation results in which some of the individuals show a crossveinless phenotype. If these individuals are selected and their pupae exposed exposed to heat again after a few generations a some individuals show the crossveinless phenotype even if their pupae have not been exposed to heat (green arrows).

References

1. Jonathan M W Slack, Conrad Hal Waddington: the last Renaissance biologist?, Nature Reviews. Genetics 3, Nr. 11 (November 2002): 889-895.