Modification of gene suppression in Drosophila melanogaster by sex chromosomes: I. Effect of the Y chromosome on variegation in malpighian tubules of wm4 larvae

Abstract

SUMMARYThe effect of the Y chromosome on white variegation associated with In(1)w"4 has been investigated by comparing the occurrence, proportion and distribution of colourless cells in the Malpighian tubules of XO, XY and XYY larvae cultured at 25°C or 15°C. The results confirmed previous observations that the Y chromosome suppresses variegation, and showed that its loss from the XY complement has a much greater effect on the proportion of colourless cells than its addition. The variegation is markedly more affected by Y-chromosome constitution than by culture temperature. Colourless cells are non-randomly distributed within and between tubules; neither chromosome constitution nor temperature appears to modify these distribution patterns.

Modification of gene suppression in Drosophila melanogaster by sex chromosomes: II. Variegation in eyes of wm4 males

“…Some preliminary observations on the eyes of Wm4 flies from a strain used for studies on Malpighian tubules (Hartmann-Goldstein and Koliantz, 1981) confirmed the fine-spot variegation initially reported in m4 (Muller, 1930) but suggested that neither as regards pattern nor gradient could the variegation be allocated unequivocally to either of the types cited above-a conclusion also reached by Becker (1978). Furthermore, the disparate descriptions of wm4 eyes to be found in the literature seem to imply an unusual variability in the expression of the phenotype, although some of the discrepancies may be due to differences between different m4 lines (Schultz, 1943).…”

“…It has already been pointed out in the previous section and elsewhere (Hartmann-Goldstein and Koliantz, 1981) that Y chromosome constitution is a more potent modifier of m4 position effect than culture temperature. Also of relevance are the asymmetric shape of the eye itself and the observations that sensitivity varies round the edge of the eye and that the most sensitive region is more or less in the middle.…”

“…were then crossed with w males (our criterion for the selection of flies with the desired genomic constitution is given in Hartmann- Goldstein and Koliantz, 1981). F2 males showing white-variegated or predominantly wild-type eyes were selected and presumed to have either one or two Y chromosomes; investigation showed that those with the additional Y chromosome had, in general, markedly fewer colourless ommatidia than the males with only one.…”

Modification of gene suppression in Drosophila melanogaster by sex chromosomes 3. Heterochromatisation associated with the wm4 phenotype

“…The stocks and breeding programmes used for our phenotypic studies of m4 variegation, more fully described in Hartmann-Goldstein and Koliantz (1981), were again employed. Male larvae with the normal sexchromosome constitution were taken from strain In(1)wm4.…”

“…An alternative, albeit less direct, approach is to analyse the phenotype of affected organs and heterochromatisation in the same strain. We recently obtained quantitative information on white-variegation in Malpighian tubules and eyes of males carrying In(1)wm4 (Hartmann-Goldstein and Koliantz, 1981;Koliantz et a!., 1984). The present paper deals with observations on the salivary gland chromosomes of wm4/yY, wm4,/y and wm4/O larvae in relation to some of the questions arising from phenotypic studies.…”