Bicoid mutants are missing the anterior region

The Bicoid (bcd) maternal-effect gene affects the anterior part of the developing larva. These photomicrographs are of Drosophila larvae that have been prepared to show their hard exoskeletons. Dense structures, such as the segmental denticle bands, appear white. (Left) A normal larva. (Right) A larva from a homozygous bcd mutant female. Head and anterior thoracic structures are missing.

[From C. H. Nüsslein-Volhard, G. Frohnhöfer, and R. Lehmann, “Determination of Anteroposterior Polarity in Drosophila,” Science 238, 1987, 1678. Reprinted with permission from AAAS..