Canalisation of development of scutellar bristles in Drosophila by control of the scute locus.

摘要: sex-linked mutant scute (sc), its noma1 allele, and a number of minor Tf:nes which can be shown to exist by selective breeding, form developmental system determines the bristles on scutellum Drosophila mlanogaster. In unselected stocks almost all flies grow four when one or two + genes are present at locus; that is, development is canalised this level phenotype. The average in sc males less than sc/sc females more one, but there considerable variation about these means. segregating for +, selected high bristle number, may mean seven eight bristles. There means also. stocks, between three bristles, most individuals having some three, few very two. scutellar phenotype controlled If does not reach as four, it varies lower controlled. fall low higher But wide variety genotypes, despite widely different en~ronmen~al conditi~ns, con~olled exactly we write P = (p (M) where phenotype, 111 Make forms tends 9 function relating M, control operates over range M values equivalent extent 60 M. # represented line horizontal axis vertical P, with slope 45" plateau 6aM long followed 45". 4 value anywhere under plateau. Figure 1 shows such curve 111. A similar based fewer points was described an equation containing six terrns (RENDEL 1959b). Fuller discussion found elsewhere 1962). receives contributions from locus scattered genome. evidence suggesting major gene comparison sc/sc, sc/-i- +/+ levels background difference sc/+ much greater +/+. second contributes first so presence +- active sc. suggestion activity negative feedback control. product until turned right off.