Several biology students are counting kernels in an ear of corn. They count a total of 420 kernels: 242 purple wrinkled, 84 purple smooth, 70 yellow wrinkled, and 24 yellow smooth. What is the ratio of kernel phenotype in this case? A) 3:2:2:1 B) 8::4:2:1 C) 9:3:3:1 D) 24:8:7:2

The answer is C) 9:3:3:1

This looks like a dihybrid cross where the expected phenotypic ratio is 9:3:3:1. However, in nature, the numbers cannot be absolut. Let's check it out:

242 purple wrinkled

84 purple smooth

70 yellow wrinkled

24 yellow smooth

Divide all by the smallest number:

242 purple wrinkled / 24

84 purple smooth / 24

70 yellow wrinkled / 24

24 yellow smooth / 24

We have

10.1 purple wrinkled which is near to 9

3.5 purple smooth which is near to 3

2.9 yellow wrinkled which is near to 3

1 yellow smooth