Drosophila melanogaster is a small fruit fly that is often used in research on genetics. Wild fruit flies normally have dark red eyes due to the presence of a brown pigment, ommochrome, and a bright red pigment, drosopterin. Fig. 2.1 shows an adult female fruit fly and an adult male fruit fly. [Figure 2.1] A biologist carried out an investigation to determine the roles of two genes that are involved in the determination of eye colour in adult fruit flies. Both genes have two alleles. Earlier research by other scientists suggested that: • the synthesis of the brown pigment ommochrome depends on the gene B/b • the synthesis of the bright red pigment drosopterin depends on the gene R/r. The biologist obtained the parent fruit flies shown in Table 2.1. Table 2.1 parent fruit flies | genotype | phenotype -----------------|----------|------------- female | BBrr | brown eyes male | bbRR | bright red eyes