Abstract
The tilt ( tt ) mutation first described by Morgan and Bridges in 1915 has adult visible phenotypes in wing posture and vein formation. We have mapped tt to a genomic region within the sosondowah ( sowah ) gene that houses the cis-regulatory elements that control expression of the Iroquois Complex genes araucan ( ara ) and caup olican ( caup ) in the wing hinge and wing veins. Sequence analysis of the tt(1) allele has identified a gtwin retrotransposon containing su(Hw) insulator binding sites within this region of sowah . We find that mutations in su(Hw) suppress the tilt phenotype, providing a potential mechanism for the insertion to affect the function of the Iroquois Complex.