Recent studies with the fruitfly Drosophila suggest that alleles of loci known from classical genetics can make major contributions to continuous-trait variation.

Khoury et al. (Am J Hum Genet 1988;42:89-95 and Am J Epidemiol 1993;137:1241-50) presented an epidemiologic approach to examine genotype-environment interaction in situations where the disease is either present or absent. In this article, the author extends the approach of Khoury et al. to quantitative outcome variables. This extension is relevant for diseases that are extremes on a continuum o...

A simulation study was performed to see whether selection affected quantitative trait loci (QTL) mapping. Populations under random selection, under selection among full-sib families, and under selection within a full-sib family were simulated each with heritability of 0.3, 0.5, and 0.7. They were analyzed with the marker spacing of 10 cM and 20 cM. The accuracy for QTL detection decreased for t...

The scanqtl function, while completely flexible and so suitable for most purposes, is rather cumbersome to use. Our most important additions are the functions addqtl, to scan for a single QTL to be added to a multiple-QTL model, and addpair, to scan for a pair of QTL to be added to a multiple-QTL model. The output of these functions is of the forms produced by scanone and scantwo, respectively,...

Variation in vein position and wing shape of Drosophila melanogaster depends on many genes. In the following, we report the results of a QTL analysis of wing shape in D. melanogaster. We identified QTL responsible for natural variation for wing shape and analyzed their interactions with developmental genetic signaling pathways important for vein positioning. The QTL analysis indicated that the ...