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| Modern Genetic Analysis Chapter 16. The Genetic Basis of Development Forming Complex Pattern: Establishing Positional Information Genetics In Process 16-4: Studying the BCD gradient The bcd "anterior-less" mutant phenotype can be rescued by wild-type cytoplasm or purified bcd+ mRNA. (a) In embryos derived from bcd mothers, the anterior (head and thoracic) segments do not form. (b) If anterior cytoplasm from an early wild-type donor embryo is injected into the anterior of a recipient embryo derived from a bcd mutant mother, a fully normal embryo and larva are produced. Cytoplasm from any other part of the donor embryo does not rescue. (c) bcd+ mRNA injected into the anterior of an embryo derived from a bcd mutant mother also rescues the wild-type segmentation pattern. (Ab = abdomen; He = head; Th = thorax.) A bicoid larva is shown in the photomicrographs. (Adapted from C. Nüsslein-Volhard, H. G. Fronhüfer, and R. Lehmann, Science 238, 1987, 1679.)

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