Very little ventral cell invagination is seen by mid to late germ band extension.
Ventral furrow fails to form.
sna2/Tp(2;1)Scorv23 adult escapers are occasionally produced, which often have missing halteres or show a hemithorax phenotype. Homozygous embryos fail to form a ventral furrow. Cephalic furrow formation, invagination of the endoderm and germ band elongation do take place in these embryos. Embryos show varying defects in the segmental denticle belts.