Many of the genes ofDrosophila melanogasterhave their transcripts deposited in developing oocytes. These maternally loaded gene products enable an otherwise homozygous mutant embryo to survive beyond the first stage of development for which the gene product is required. Zygotic mutations that disrupt the Hedgehog signal transduction pathway typically yield a segment polarity ‘lawn of denticles’ cuticle phenotype. However, an embryo homozygous mutant for a gene can achieve normal embryonic segmentation precluding classification of the gene as a component of the Hh pathway, if wild-type transcripts from the mother are present. This chapter discusses the theory and importance of analyzing germline clone embryos for maternally acting genes involved in Hh signal transduction, and describes in detail the method to generate mutant germline clone embryos.
