Gynandromorph analysis of the thoracic disc primordia in Drosophila melanogaster

Cell lineage relationships observable in Drosophila gynandromorphs have been used to locate the primordia of the individual thoracic disc relative to each other in the embryo. Three observations indicate that the borders of the individual disc primordia lie very close to each other, separated by few if any non-disc cells. First, the frequency of mosaicism within each disc indicates large primordia, of similar magnitude to the distances between the centres of adjacent primordia. Second, very few XX/XO-borders cut between adjacent discs without also cutting into one or the other disc. Third, sturt distances between points on adjacent discs are often much smaller than distances measured within individual discs. The proximity of disc primordia suggests that the individual discs might share common precursor cells in the early embryo.