Chapter 4, Problem 7EQ

Duroc Jersey pigs are typically red, but a sandy variation is also seen. When two different varieties of true-breeding sandy pigs were crossed to each other, they produced ${\text{F}}_{\text{1}}$ offspring that were red. When these ${\text{F}}_{\text{1}}$ offspring were crossed to each other, they produced red, sandy, and white pigs in a 9:6:1 ratio. Explain this pattern of inheritance.