DOC AND COPIA INSTABILITY IN AN ISOGENIC DROSOPHILA-MELANOGASTER STOCK

A high degree of heterogeneity and an overall increase in number of in sertion sites of the mobile elements Doc and copia were revealed in on e substock of an isogenic Drosophila melanogaster stock, while in two other substocks the distribution of copia sites was highly homogenous, but that of Doc sites was again heterogenous. We therefore concluded that copia was unstable in one of the substocks and Doc was unstable i n all. Doc instability presumably arose earlier than copia instability . Doc and copia transpositions were directly observed in experiments w ith one substock. An abundance of copia insertions was revealed in the X chromosome where insertions with deleterious effects are exposed to selection in hemizygous condition. The locations of many other mobile elements (mdg1, mdg2, mdg3, mdg4, 297, B104, H.M.S. Beagle, I, P, BS, FB) were found to be conserved in each substock and did not differ be tween them, indicating that these mobile elements were stable. This ho mogeneity is a strong argument against any possibility of inadvertent contamination.