No sequence alteration compared to wild type has been found in the coding region or in the splice junctions.
Mutant embryos do not show defects in muscle attachment. The mutant embryos show strong defects in midgut development.
80% mutants hatch but all die before the third instar stage. Embryos and a proportion of hatched larvae exhibit defects in the gut but normal muscles. Those larvae with normal guts survive the longest until second instar when they start to show some muscle detachment. Mutants that die as embryos have defective ventral cord condensation. Mitotic clones in the wing produce bubbles. All double heterozygotes with mysxR04 survive.
if2B1 is partially rescued by ifminigene
Class III mutation.