The X and 4th chromosome nondisjunction defects seen in FM7/X females heterozygous for Df(3L)66C-T2-10 are largely rescued by expression of mtrmSAM-del.Scer\UAS.T:Zzzz\FLAG under the control of Scer\GAL4nos.UTR.T:Hsim\VP16 (nondisjunction rates are 4.9% and 1.5% respectively in the rescued flies, compared to 0.9% and 0.9% in controls).