الفهرس 
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Abstract
The X-linked mutant zeste has the unusual effect on giving lemon yellow colour only in females. This mutation has no effect on the eye colour of males. The difference is due to the difference in the w+ loci, females have two w loci, while the males have only one. However, males with two copies of w+ show the mutant phenotype (lemon yellow), whereas females with one copy of w are wild type.
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Mitotic recombination between the centromere and the outside marker leads, when induced in larvae, to twin mosaic spot in adult flies. The phenotype of each twin partner depends on the genotype of the recombinant cell from which it develops. In the case of zw/zw females mitotic recombination at almost any place along the X—chromosome leads to yellow/white twin spot. In the case of zw+ males, which have normal red eyes, mitotic recombination between the X and the Y chromosomes yields a yellow single spot, since the twin cell most probably die, not having any X_euchromatin
The original idea of the present work was to design a more efficient system for mutagenicity testing by using different genotypes of zeste males and females which have