Effect of Zeste on White Complementation
The locus in which we are most interested is the white locus; it is on the first chromosome and maps at 1.5 map units. There are five recombinationally separable sites known in this locus (Judd, 1964). The site which maps right-most is called white-spotted (w sp ); the white (w) allele which has a pure white eye color as well as white-cherry (w ch ) which has a translucent pink eye phenotype also map at the next right-most site. Basically, white forms a single complementation group with the exception of w sp ; i.e. all white mutants fail to complement each other with the exception of w sp . The phenotype of w sp itself is unusual compared to other white mutants; w sp males and females have spotted eyes of yellowish to brown pigment facets in a light color background. We are here interested in the fact that the w sp mutation partially complements all other white mutations. This is clearly seen in the case of w/ w sp and w ch /w sp flies; both these trans-heterozygotes have uniformly pigmented brownish red eyes approaching the wild type. The new observation we have made is that this complementation between w sp and other white alleles depends on the allelic conditions of the zeste locus, where zeste is also a mutation on the first chromosome at 1.0 map units. Before we describe our observation, we will briefly summarize what is known about mutations at the zeste locus.
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