An amorphic allele exhibiting loss of zygotic hb function with an antimorphic effect with respect to maternal hb function.
Homozygotes and heterozygotes with a wild type copy display a severely reduced head, up to three abdominal segments are formed in the head region.
Lacks gnathal and thoracic segments. Irregular shape denticle bands are formed from anterior to posterior abdomen, are of correct polarity.
Homozygous embryos lack labium and all thoracic segments; head and gnathal segments transformed into posterior abdominal segments as is A1. Expressed only in homozygotes, not in hemizygotes; hb7 hemizygotes displays class III phenotype. Lethality of hb7 homozygotes not rescued by Dp(3;Y)P92 which is able to cover the other alleles; attempts to implicate a linked lethal mutation negative.