In fruit flies, grey body (G) is dominant to black body (g), and long wing (L) is dominant to vestigial wing (l). Flies heterozygous for both genes were crossed. The 320 offspring were counted and compared with the expected 9 to 3 to 3 to 1 ratio using the chi-squared test.
| Phenotype | grey long | grey vestigial | black long | black vestigial |
|---|---|---|---|---|
| Observed number | 172 | 66 | 58 | 24 |
| Degrees of freedom | Critical value (p = 0.05) |
|---|---|
| 2 | 5.99 |
| 3 | 7.81 |
| 4 | 9.49 |
Calculate the value of χ2. Show your working.
[3]
Using the critical value, deduce whether these results are consistent with the two genes assorting independently.
[2]