You produce an F2 generation from pure breeding green and yellow peas that has 35 yellow and 5 green offspring. Conduct a Chi-squared test. The critical value in the Chi squared table is 3.84. Are your results consistent with autosomal dominance?

If the trait is autosomal and one allele is dominant over the other, there will be a good fit of the observed phenotypic proportions to the expected 3:1 ratio:

- Parental generation: pure breeding green (yy) x yellow (YY)

- F1: Yy

- Expected F2 frequencies as a result of F1 self-breeding: 3/4 Y_ (yellow), 1/4 yy (green).

The Chi squared test needs the observed and expected number of individuals.

The Expected F2 number of individuals is calculated by multiplying the expected frequencies by the total number of individuals in the offspring (35+5=40).

-Expected F2:

3/4 × 40 yellow = 30 yellow

1/4 × 40 green = 10 green

- Observed F2: 5 green, 35 yellow

[tex]X^2=[/tex]∑ [tex]\frac{(Observed-Expected)^2}{Expected} [/tex]

[tex]X^2= \frac{(35-30)^2}{30} + \frac{(5-10)^2}{10} \\\\X^2 = 3.33[/tex]

The Chi squared value is smaller than the critical value. We fail to reject the hypothesis of good fit to the 3:1 ratio, therefore the results are consistent with autosomal dominance.