Homozygotes/hemizygotes are posterior crossveinless.
Heterozygotes show a direct effect on the shape of the wing, having a significant effect in the posterior region (mostly shifting the position of the posterior crossvein relative to wild type), but no effect in the anterior region.
Homozygotes lack typically lack most or all of the posterior crossvein.
cv-2k03511/cv-2225-3 has posterior crossvein phenotype, enhanceable by gbb4
The addition of gbb4 to cv-2225-3/cv-2k03511 animals produces an enhancement of the posterior crossvein phenotype seen in these flies.