Males and homozygous females are semi-lethal. Surviving flies have reduced rough eyes, bristles on the thorax and head are sometimes missing, wings are abnormal with a thin texture and thickened veins.

large clones; y Sb⁺ clones; mitotic nondisjunction Semilethal as males or homozygous females; surviving flies have reduced roughened eyes, bristles on the head and thorax sometimes missing, abnormal wings with thin texture and thickened veins; both sexes sterile. Up to 100 fold increase in the incidence of mwh clones per wing in mit15;mwh/+ flies raised at sub-restrictive temperature. Half of all metaphases in larval ganglion cells are hyperploid for one or more chromosomes; hyperploidy for nearly all combinations of sex chromosomes and autosomes are observed. Chromosome breakage seen in less than 2% of cells.