Cathy and Doug Both Have Brown Eyes

Multiple Choice

Cathy and Doug both have brown eyes. If their child has blue eyes, what can we conclude about Cathy's and Doug's genes for blue eyes?

A) Both Cathy and Doug must be carrying a recessive gene for blue eyes.
B) Either Cathy or Doug must be carrying a recessive gene for blue eyes.
C) Both Cathy and Doug must be carrying a dominant gene for blue eyes.
D) Either Cathy or Doug must be carrying a dominant gene for blue eyes.