Subject: Official to FlyBase
The mirr/cre/DH/B12/Sai/sai alleles on the D1 and D3 chromosomes are
different as judged by viability of heterozygotes with Henry Sun's DH-1
allele (which is itself hypomorphic for the viability effect
since it is homozygous viable, though with recessive outheld wings and
reduced alulae, once the extraneous lethal(s) had been crossed off). D1
on CxD/DH is completely lethal; D1 on DcxF gives 4% escapers/DH (the
two D1 chromosomes differ in extent of head defects -- DcxF in most
genotypes has none, but they become dramatic over DH). D3/DH is, on
the other hand, nearly completely viable (85-96% relative to the two
balancer sib classes), with milder head defects (D3 itself has reverted
that phene) but with missing bristles (not a dominant phene of D3, is a
recessive phene of some other allele). Since D3 is still lethal over
other alleles (eg, Sai1 and Sai2) it still carries a mutant allele of
the 69D gene, but that allele is clearly different from the one carried on
the parent D1 chromosome.