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Abstract
We have used the expression patterns of genes known to be important during early Drosophila
development to determine the segment-parasegment organization of the genital discs
and to localize the three primordia in the male and female genital discs, engrailed
(en) and hedgehog (hh) were used to locate posterior compartments in A8-A10, while
cubitus interrupts (ci) localized the anterior compartments for each segment, decapentaplegic
(dpp) identified the anterior cells that abut en and hh at the anterior-posterior
border. abdominal-A (abd-A) identified the anterior compartment for abdominal segment
8 (aA8) in females but was not detected in the repressed female primordium in male
discs. Abdominal-B (Abd-B) was expressed throughout the discs except for a small area
along the edge of the posterior lobes, leaving open the possibility that A11 may contribute
to the genital discs, caudal (cad) was expressed segmentally in the anal primordium
of A10, extending through the Abd-B unstained region, wingless (wg) and gooseberry
(gsb) may have assumed an added role in the discs perhaps providing proximal-distal
cues. Models are presented to show how the segments and parasegments may fuse together
during embryogenesis to form the mature male and female genital discs.