Homework Sourse1 In corn purple aleurone is dominant to red yellow endosper
1. In corn, purple aleurone is dominant to red, yellow endosperm is dominant to white, round kernels is dominant to wrinkled, and solid green leaves is dominant to striped. If you made the following cross, what proportion of the offspring would have red aleurone, yellow endosperm, wrinkled kernels and solid green leaves?
Pp yy Rr ss x Pp Yy Rr Ss
2. You have obtained data from a cross between two corn plants and you have performed a Chi-square test for the hypothesis that data fit a 2:1:1 ratio of yellow: purple: red color. Your chi-square value is 4.90. Answer the following questions:
a. Based on the Chi-square table below, draw a conclusion about your hypothesis (reject or fail to reject).
b. Circle the relevant cutoff chi-square value in the body of the table.
X^2 Table
d.f Probability
p=0.9 p=0.5 p=0.2 p=0.05 p=0.01 p=0.001
1 0.02 0.46 1.64 3.84 6.64 10.83
2 0.21 1.39 3.22 5.99 9.21 13.82
3 0.58 2.37 4.64 7.82 11.35 16.27
4 1.06 3.36 5.99 9.49 13.28 18.47
5 1.61 4.35 7.29 11.07 15.09 20.52
Solution
Pp yy Rr ss x Pp Yy Rr Ss
red aleurone (pp), yellow endosperm(Yy or YY), wrinkled kernels (rr) and solid green leaves (Ss or SS)
Possible Genotype for the above trait: ppYyrrSs or ppYYrrSS or ppYyrrSS or ppYYrrSs
Four trait = 8 alleles = 2n = 28 =256 possibilities
probability of a homozygote = 1/4 and for heterozygote is 2/4 =1/2
ppYyrrSs = 1/4 x 1/2 x 1/4 x 1/2 = 1/64
ppYYrrSS = 1/4 x 1/4 x 1/4 x 1/4 = 1/256
ppYyrrSS = 1/4 x 1/2 x 1/4 x 1/4 = 1/128
ppYYrrSs = 1/4 x 1/4 x 1/4 x 1/2 = 1/128
1/64 + 1/256 + 1/256 + 1/128 = 8/256 = 1/32
Therefore proportion of the offspring would have red aleurone, yellow endosperm, wrinkled kernels and solid green leaves = 1/32
2. a) three traits so degrees of freedom = n -1 = 3-1 = 2
chi-square value is 4.90 which is less than p value of 0.05 so accept the hypothesis
2b)
d.f Probability
p=0.9 p=0.5 p=0.2 p=0.05 p=0.01 p=0.001
1 0.02 0.46 1.64 3.84 6.64 10.83
2 0.21 1.39 3.22 5.99 9.21 13.82
3 0.58 2.37 4.64 7.82 11.35 16.27
4 1.06 3.36 5.99 9.49 13.28 18.47
5 1.61 4.35 7.29 11.07 15.09 20.52
