Mutants have a rough eye phenotype with minor defects in ommatidial assembly.
Heterozygotes and homozygotes appear wild-type, although homozygotes can show a phenotype as extreme as ast1/ast1 under unfavourable culture conditions.
Phenotypically wild-type. Enhances expression of S1 in heterozygotes. S1/ast4 has smaller eye than S1/+; resembles ast1/ast1 in wing phenotype. RK3.