Genetic analysis ofloboid-ophthalmoptera,a homoeotic strain inDrosophila melanogaster

A homoeotic strain in which wing-like outgrowths are produced from the eye region was investigated. The actual wing nature of the malformation was confirmed. Genetically, this homoeotic character depends on the presence of an eye-reducing factor,loboid (ld; 3–102), and of modifier genes. One important sex-linked modifier, probably located at 1–5±, is thought to be the main factor underlying the homoeotic effect. It is designated asopht (ophthalmoptera), and the mutant strain asld-ophtKobel (1968), assuming a specific allele ofld with homoeotic effect, originally described this strain under the nameld^oph. It is shown that inld-opht, theld factor can be replaced byDfd^r-L (3–47.5) without irrevokably losing the homoeotic effect.Penetrance and expressivity ofopht are very variable and subject to genetic and environmental changes, and they readily respond to selection. Such properties are common to all homoeotic mutants. The phenomenon of homoeosis is interpreted in terms of allotypic differentiations resulting from a switching of development into other epigenetic pathways. This switching is perhaps due to an altered rate of proliferation.Aided by a grant from the Netherlands Organization for the Advancement of Pure Research (Z.W.O.).