Penetrance of the axon tracts defects in mid mutants.

Embryos were stained with BP102 (for stalling) and Fas II (for midline crossing and peripheral projection) and examined for axon guidance defects. Star (*) indicates approximation of number of hemisegments counted since it is impossible to count the hemisegments accurately in these mutants (sli and robo) due to the collapsing of tracts at the midline. Number sign (#) indicates parents without any balancers (mutant flies were crossed to wild type and the progeny males and females carrying the mutant chromosome over wild type chromosome from this cross were inter-crossed to generate homozygous mutant embryos). The remaining genotypes were all obtained from balancer-bearing flies. Note that a given hemisegment can have all the three scored phenotypes.