1. A large ear of corn has a total of 433 grains, including 271 purple & starchy, 73 purple & starchy,
63 yellow & starchy, and 26 yellow & sweet.
HYPOTHESIS: This ear of corn was produced by a dihybrid cross (PpSs X PpSs) involving two pairs of heterozygous genes resulting in a theoretical (expected) ratio of 9:3:3:1.
Test your hypothesis using Chi-square and probability values. SHOW YOUR WORK!

2. PHENOTYPE
OBSERVED
EXPECTED
Purple & starchy
271
433 X 9/16 =
Purple & Sweet 73
433 X 3/16 =81.19
Yellow & Starchy 63
433 X 3/16 = 81.19
Yellow & sweet 26
433 X 1/16 = 27.06
TOTAL
433
( )2 + ( )2 + ( )2 + ( )
X2= = 74.18

3. df = 4-1 = 3
0.5 probability = 7.82
X2 = 74.18
Reject the null hypothesis. Not a 9:3:3:1 cross