Thoracic abnormalities in tumorous-headDrosophila melanogaster.

Developmental-genetic properties of thoracic abnormalities are described intumorous-head (tuh-1; tuh-3) Drosophila melanogaster. Approximately 7% of females from an unselected strain have abnormal thoracic appendages (primarily metathoracic) ranging from missing to duplicated. When multiple, these abnormalities are generally unilateral and contiguous. Results of reciprocal crosses indicated that, as with head defects, thoracic defects are maternally affected. A major modifier,enhancer of tuh-1, of the maternal effect shifts the distribution of thoracic defects anteriorly and increases the frequency of head defects. We suggest that thetumorous-head system illustrates a genetic influence over an anterior-posterior gradient inD. melanogaster.