In interspecific bwD
heterozygotes (in which D.melanogaster bwD
has been introgressed into the D.simulans
background and backcrossed to D.simulans
for six generations), the 59E region does not associate with the X chromosome heterochromatin, but does associate with the second chromosome heterochromatin, in interphase nuclei of larval central nervous system cells.
Syncytial blastoderm embryos have gaps in the field of nuclei and many nuclei have fallen into the interior of the embryo. Typically, these interior nuclei are in pairs connected by a thin thread of chromatin. The frequency of these defects is 4 to 16-fold higher than in wild-type embryos.
PEV is observed as the very strong dominant variegating effect on the bw+
copy present on the homologous chromosome. Heterozygotes with Df(2R)bw5
exhibit about 2% eye pigmentation.
Eye color varies with age from purple to brown. Shows slight variegation in combination with st
). Wings pebbled. bwD
/+ shows nearly a 100-fold reduction in pteridine levels. bwD
/+ > bwD
in severity of effect (FBrf0050859
). Variegation suppressed by extra Y chromosomes (FBrf0012497
). Homozygote viable and fertile. Larval Malpighian tubules bright yellow (FBrf0005752