hypomorphic allele - genetic evidence

Exon sequencing of the hbs gene failed to identify unique polymorphisms in the a69 mutant that are absent in phenotypically wild-type control strains. However, based on the failure of the a69 allele to complement four of fives tested hbs alleles and the observation that all eleven heteroallelic combination of four alleles of hbs display the a69 mutant phenotype of a reduction in the fraction of R8 photoreceptor cells expressing Rh5, the data is consistent with the a69 mutation being an allele of hbs, hbs^a69.

Recombination and excision analysis demonstrates that the hbs^a69 mutation which results in a reduction in the fraction of Rh5-expressing R8 photoreceptor cells in the eye is not caused by the P{etau-lacZ}a69 insertion on the same chromosome.