Molecular Dissection of a Major Gene Effect on a Quantitative Trait: The Level of Alcohol Dehydrogenase Expression in Drosophila melanogasterGenetics 144 1559-1564 (December, 1996)
A molecular mapping experiment shows that a major gene effect on a quantitative trait, the level of alcohol dehydrogenase expression in Drosophila melunogaster, is due to multiple polymorphisms within the Adh gene.
These polymorphisms are located in an intron, the coding sequence, and the 3‘ untranslated region. Because of nonrandom associations among polymorphisms at different sites, the individual effects combine (in some cases epistatically) to produce “superalleles” with large effect.
These results have implications for the interpretation of major gene effects detected by quantitative trait locus mapping methods. They show that large effects due to a single locus may be due to multiple associated polymorphisms (or sequential fixations in isolated populations) rather than individual mutations of large effect.
[This classic paper uses P‑element transformation to show that three separate molecular polymorphisms in alcohol dehydrogenase affect the level of gene expression, that these polymorphisms interact epistatically and that the polymorphisms have opposite effects on expression.]
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