Deletion of the PRD (His-Pro) repeat.
One copy of prd+mXa fully rescues the cuticle phenotype of prd4 homozygous embryos. Two copies of prd+mXa fully rescue prd4/Df(2L)Prl animals to adulthood, while one copy partially rescues prd4/Df(2L)Prl viability. One copy of prd+mXa partially rescues the fertility of prd4/Df(2L)Prl males, while two copies fully rescue the phenotype.