Miocene Deposits in the Amazonian Foreland Basin

(1 1). 59. K. D. Donaldson and G. H. Karpen, unpublished results. 60. In cases where partners were marked with the same genetic marker (most of Fig. 2B), disomic animals could not be positively identified in the F1 generation. Therefore, in each experiment a large number (30) of randomly selected ry+ or y+ F1 progeny (which includes both 1 Dp and 2 Dp animals) were outcrossed to XAY, y/O; ry506 males. The 2 Dp F1 animals used to estimate disjunction frequencies were identified by observation of high transmission rates in the F2 scoring generation. Nondisjunction rates were calculated as above, except that the nondisjunction class was determined by doubling the number of 0 Dp animals in the F2 generation. This correction was necessary because the 2 Dp nondisjunction progeny could not be distinguished phenotypically from the 1 Dp class in these crosses. The fact that recovery of the 0 Dp and 2 Dp classes did not differ significantly when both classes could be monitored independently strongly validates the use of this correction. Furthermore, outcrossing the F2 ry+ progeny from putative y1230/y1230 F1 animals demonstrated that the F2 progeny contained equal numbers of 0 Dp and 2 Dp animals (G. H. Karpen et al., data not shown). This result confirmed both the disomic nature of the Fl parents and the appropriateness of using the 0 Dp class to estimate nondisjunction. 61. Animals with two differentially marked minichromosomes and zero, one, or two copies of the P(nod+) transgene (19) were generated from the cross y; P(nod+)/SM1, Cy; ry; 31E, y+ females xy/Y; P(nod+)/ Sp; ry; J21A, ry+ males (or 20A or lOB). The y; P(nod+)/Sp; ry female progeny provided the 2E+1T class, and the 2E+2T females were the y; P(nodl)/ P(nod+); ry siblings. The J21A monosome siblings (yry+) were used for the transmission tests, whereas the 31E/J21A, 31E/1OB, and 31E/20A disomes (y+ ry+) were used in the nondisjunction tests. The 2E+OT control ND frequencies were taken from the data in Fig. 2A, because independent analyses demonstrated that the SM1 balancer raises nondisjunction frequencies significantly. For the J21A monosome transmission tests, the 2E+OT class used in the transmission assay were produced by the cross y; ry; J21A, ry+ females x y/Y; P(nod+)/ Sp; ry males. All test females were crossed and the results analyzed as described (56, 57). 62. T. Murphy contributed significantly to discussions and data analyses, and his efforts are gratefully acknowledged. We also thank K. Cook, R. Kolodner, T. Murphy, and D. Weigel for comments on the manuscript, K. Afshar and R. S. Hawley for the nod+ transgene stock (placW nod+-1 5), J. Simon for the artwork in Fig. 4, and A. Dernburg, J. Sedat, and S. Hawley for communicating results before publication. This research was supported by a grant from the American Cancer Society (DB-1 200), which we gratefully acknowledge.