Due to its small size, short life cycle, abundance of genetic variability, and relative inexpensiveness, Drosophila melanogaster, the fruit fly, is used as the model organism. Mendelian traits studied in the project were eye color on chromosome 1 (sex-linked trait), vestigial-wing (on chromosome 2), ebony-colored body (on chromosome 3). For one-gene segregation, the flies with red eye were wild phenotype while white these with white eye were mutant phenotype. For two-gene segregation, the flies being full wing and normal body color were wild phenotype while these being vestigial wing and ebony body were mutant phenotype. The traits for two-gene segregation were wing and body color. The crosses and reciprocal crosses were produced for one-gene and two-gene segregations. The expected overall phenotypic ratios for one-gene segregation were 3 red eye : 1 white eye in the cross and 1 red eye female : 1 white eye female : 1 red eye male : 1 white eye male in the reciprocal cross. The expected overall phenotypic ratios for two-gene segregation were the same, 9:3:3:1. The results of œá2 statistical test for one-gene segregation didn‚t fit 3:1 ratio but fit 1:1:1:1 ratio. The results of œá2 statistical test for two-gene segregation didn‚t fit 9:3:3:1 ratio in both crosses. The explanations were given regarding the variations for different types of the crosses.