Mothers against decapentaplegic is a protein from the SMAD family that was discovered in Drosophila.
During Drosophila research, it was found that a mutation in the gene in the mother repressed the gene decapentaplegic in the embryo.
The phrase "Mothers against" was added as a humorous take-off on organizations opposing various issues e.g.
Mothers Against Drunk Driving (MADD); and based on a tradition of such unusual naming within the gene research community.
[1][2][3] Several human homologues are known: