1. The Search
Begins!
Mr. Holmes and Watson arrived at the home of Lord Robert Lancaster early morning as promised. As Watson explained to Holmes, ”Old Lord Peter (Lord Robert’s father) is shown over the fireplace. As a young man, he had bright red hair. His wife Violet, was a brunette. Half their children, including the late Lord Robert, had red hair the others were brunettes. As only a recessive pair of genes (aa) will produce red hair, each of Lord Peter’s children received an (a) gene from him.”
Watson went on, We know Lady Violet had (A) genes because she was a brunette, and even one (A) gene will produce brown hair. But Lady Violet must have been heterozygous (Aa) because half her children had red hair.

2. Lord Peter Lancaster and Lady Violet Lancaster

3. Explore This: Our Story Continues…….
What are recessive genes? What are dominant genes?
When representing genes, how are recessive genes differentiated from dominant genes?
Why are two letters used to represent a trait, i.e. (aa) for red hair?
What is the rule for expressing recessive genes?
Why is only one (A) gene necessary to produce brunette hair?
What does it mean for an individual to be heterozygous for a trait?
What does it mean for an individual to be homozygous for a trait?
How would you represent homozygous dominant genes?
How would you represent homozygous recessive genes?
How can you use this information to help you solve the murder?
What other information do you need to proceed?
Our Story Continues…….

4. Reference
This activity was adapted from: