In the fruit fly, Drosophila melanogaster, eye colour and wing shape are controlled by genes. • E/e are alleles of a gene involved in eye colour. • E results in red eyes, e results in purple eyes. • N/n are alleles of a gene involved in wing shape. • N results in normal (functional) wings, n results in vestigial (short, non-functional) wings. These genes are both autosomal. A dihybrid cross was carried out between a fly with red eyes and normal wings and a fly with purple eyes and vestigial wings. Both parents were homozygous for both genes. The offspring from the F1 generation were crossed to obtain the F2 offspring. The results are shown in Table 2.1. | F2 offspring phenotype | expected number of individuals | expected F2 ratio | observed number of individuals | observed F2 ratio | |:----------------------------|:-------------------------------|:------------------|:-------------------------------|:------------------| | red eye, normal wing | 225 | | 287 | 22.1 | | red eye, vestigial wing | | 3 | 13 | 1.0 | | purple eye, normal wing | 75 | | 17 | 1.3 | | purple eye, vestigial wing | | 1 | 83 | 6.4 |