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Fig. 7. The expression domains of Drosophila and Tribolium gap
genes. Head, thorax and abdomen are separated by vertical bars. (A) Fate map
and gap gene expression in the Drosophila blastoderm. (B,C) Late
blastoderm and early germ band stages in Tribolium (the photos to the
right illustrate the stages represented by B and C). (B) In the
Tribolium blastoderm only head and thoracic segments are specified.
The posterior pole comprises the growth and patterning zone (growth z) and
probably includes terminal cells (not shown). Extra-embryonic tissue has been
omitted for simplicity. (C) During germ band growth, the posterior
giant domain splits into stripes located in segments T3 and A2, far
anterior of the segment primordia covered by Dm'giant (A). Although
anterior expression domains of gap gene orthologs appear largely conserved
(compare anterior domains of tailless, giant and hunchback),
the posterior gap domains in Tribolium are shifted relative to the
segment primordia. See discussion for further details.