Mary uses the process of baking a cake as a model to help her friend understand how genes function in people. The ingredients in Mary’s cake recipe are:

Flour
Milk
Eggs
Baking powder
Sugar
Butter
Vanilla
The cake recipe provides directions for how to mix the ingredients together, the temperature of the oven, and the length of time the cake needs to bake. The end result is a plain, yellow cake.

Use Mary’s model to explain the process of how an observable trait (such as curly hair or brown eyes) happens in people. Begin your explanation with your answer to part (a).