In the current study our theoretical and experimental work was focused on the detailed molecular analysis of the mutational DNA alterations induced by neutrons and gamma rays at the uniquely telomeric gene yellow, in the sex (X) chromosome. The yellow locus controls the melanotic pigment pattern of the cuticle of the adult fly and the pigmented mouth parts and denticle belts of the larval cuticle. yellow mutants can be separated into the following phenotypic classes, each group involving a color change [1] from gray-black to yellow-brown: (1) mutants that show a total loss of pigmentation from the cuticle (y1-type) and (2) mutants that show a mosaic pigment pattern, some regions of the cuticle being wild type and others yellow in color (y2-type). In our study we analyzed 16 lines of spontaneous mutations, 21 mutant lines induced by gamma rays, 3 mutant lines induced by neutrons and 8 mutant lines induced by combination of neutron and gamma rays. For PCR we used six pairs of primers which cover the whole gene yellow, including regulatory region [2] and terminator region [3]. As result of radiation damage in yellow gene, appear two types of phenotype, y1 and y2. The most frequently observed alteration in spontaneous and gamma-ray-induced mutants was the loss of the end of intron 1, exon 2 and the terminal region. Mutation in other region occurred less frequent. Neutrons, as high-LET radiation, produced less damage as expected.