3.A genetics engineer was attempting to cross a tiger and a cheetah. She predicted a phenotypic outcome of the traits she was observing to be in the following ratio 4 stripes only: 3 spots only: 9 both stripes and spots. When the cross was performed and she counted the individuals she found 50 with stripes only, 41 with spots only and 85 with both. According to the Chi-square test, did she get the predicted outcome

Yes, she got the predicted outcome.

Explanation:

A genetic engineer was attempting to cross a tiger and a cheetah. She predicted a phenotypic outcome of the traits she was observing to be in the following ratio: 4 (stripes only): 3 (spots only): 9 (both stipes and spots). When the cross was performed and she counted the individuals she found 50 with stripes only, 41 with spots only and 85 with both. According to the Chi-square test, did she get the predicted outcome?

Using the Chi square formula:

Where, = observed frequency (OF) and = expected frequency (EF).

Phenotype       OF             EF                            

Stripes only      50      4/16 x 176 = 44           = 0.8182

Spots only        41       3/16 x 176 =  33         = 1.9394

Stripe & spot    85      9/16 x 176 =  99         = 1.9798

Total = 4.74

Degree of freedom = 3 - 1 = 2

tabulated (p = 0.05, df = 2) = 5.99

The calculated is greater than the tabulated, hence, we conclude that she got the predicted outcome. It means there is no significant difference between the expected outcome and the observed outcome.