lethal - all die during embryonic stage
some die during embryonic stage
visible | recessive
first basal wing cell
first posterior wing cell
wing vein L3
wing vein L4
kn1/knSA1 flies have wings that lack most of the intervein space betweens veins 3 and 4, and show fusions of veins 3 and 4, particularly proximal to the posterior crossvein.