Germ cell selection in genetic mosaics in Drosophila melanogaster

Heritable mutations in the germ line lead to genetically heterogeneous, or mosaic, gonads. Many of the genes used in germ-line development also play r oles in somatic development [Saffman, E. E. & Lasko, P. (1999) Cell. Mol. L ife Sci. 55,1141-1163]. Mutations in these genes may have cellular phenotyp es throughout germ-line development leading to their differential eliminati on or survival, as has been observed in somatic cells [Morata, G. & Ripoll, P. (1975) Dev. 8ioL 42, 211-221]. We investigate whether mutations in hete rozygosis are subject to pregametic selection in the germ line. We initiate d clones of wild-type homozygous cells at different stages of development i n gonads heterozygous for eight different recessive chromosome deficiencies . Here we show that cell selection takes place in mosaic germ-line populati ons. This phenomenon represents a level of selection that precedes and cond itions subsequent zygotic selection by affecting the genes available in the gametic population.