Table 5.2 gives the observed counts for each of the four phenotypes in the F2 generation. Calculate $\chi^2$ for the F2 generation by completing Table 5.2. Use $\chi^2 = \sum \frac{(O - E)^2}{E}$ as the formula.
At $p = 0.05$ with 3 degrees of freedom, the critical value is $7.815$. Comment on whether the null hypothesis ought to be accepted or rejected.
For the F2 generation, red males with black spots, $X^R Y^R Bb$, were crossed with red females with black spots, $X^R X^r Bb$. Complete the Punnett square in Fig. 5.1 to display the genotypes and phenotypes of the F2 generation. Use $X^R$, $X^r$ and $Y^R$ for the alleles of the gene that controls body colour. Use $B$ and $b$ for the alleles of the gene that controls whether black spots are present or absent.
Explain why there are no white males or males that are white with black spots in the F2 generation.
In a different cross, red males with genotype $X^R Y^R bb$ were mated with white females with genotype $X^r X^r bb$. All male offspring were predicted to be red and all female offspring were predicted to be white. The observed outcome included two red females out of 253 and one white male out of 198. Suggest an explanation for this unexpected result.