Table 1.

Analysis of Rap1^R:Rap1⁺ mosaic facets

R cell	Fraction w+ Rap1R observed
R8	0.38
R2	0.42
R5	0.43
R3	0.40
R4	0.38
R1	0.38
R6	0.33
R7	0.19

Clones of homozygous w⁻Rap1⁺ cells were induced in a w⁺Rap1^R/w⁻Rap1⁺ background. R-cells in 74 genetically mosaic and phenotypically wild-type facets at the clone borders were scored for the presence (w⁺) or absence (w⁻) of pigment granules. In Rap1^R/Rap1⁺ eyes, 25% of facets are phenotypically wild type (15), meaning that 25% of each R-cell type in the mosaic facets will be w⁺ or w⁻ randomly. Thus, a particular R-cell in a phenotypically wild-type facet will be w⁺Rap1^R at a frequency of 13%, even if Rap1^R produces its mutant phenotype by functioning within that R-cell. Conversely, if Rap1^R does not function within a particular R-cell, that R-cell should be w⁺Rap1^R at a frequency of 50%. χ² analysis was used to evaluate whether the observed frequencies for each individual R-cell are significantly different from 0.50 (R8, 2, 5, 3, 4, 1, or 6) or 0.13 (R7). Only the observed frequencies for R6 and R7 are significantly different from 0.50 and 0.13, respectively. Some of the w⁺ cells may have been contained within the twin spot of the w⁻Rap1⁺ clone and, thus, are homozygous for w⁺Rap1^R. This should have little effect on the interpretation of the experiment as Rap1^R homozygotes have nearly the identical photoreceptor patterning phenotype to Rap1^R+ (15).