Polytene chromosomes normal.
Deletion of most of the H coding region.
Bristle loss on head and notum and double socket phenotype.
H18 is a suppressor of phenotype of Brdunspecified
Dominant suppressor of Brd: due to haploinsufficiency.
Posakony/Groger.
Strong H allele.
Phenotypic series of H alleles correlates with severity of molecular defects: in order of decreasing severity H18 = H20 > H21 > HD179.