Polytene chromosomes normal.
Lethality occurs in the late embryonic and first larval instar stages. The majority of hemizygotes die as embryos with normal cuticular morphology.
Complements the viable cos alleles, unless flies are simultaneously heterozygous for "Cos" mutants.
Grau & Simpson.
Detected in a screen designed to detect mutations lethal when transheterozygous with cosV1, Pka-C1Cos-3.
Allelic series: cos3 >= cos2 >= cos1 = cos4 = cos5 >= cos6 >= cos7. No germ-line clones homozygous for cos3 were recovered, perhaps indicative of a second mutation on the chromosome.