Homozygous embryos exhibit defects in posterior pattern.
Class 1 allele: Unrescued embryos (lacking maternal and zygotic phl activity) fail to differentiate into structured embryos and degenerate around 7 hrs of development. Rescued embryos (carrying wild type phl from their father) miss most structures posterior to abdominal segment 6 or 7 and anteriorly a portion of the cephalopharyngeal skeleton, labral sense organ and medial tooth are deleted. fkh expression (in wild type evident in hindgut, Malpighian tubule(s) and anal pads) entirely absent from class 1 embryos. Expression of tll, hkb, hb, fkh absent from both rescued and unrescued embryos, 7th ftz stripe deleted and 6th ftz stripe variably deleted/expanded. Conclude from 0% to 20--25% EL of blastoderm embryos deleted in class 1 alleles.