I am currently working on understanding Hardy-Weinberg Equilibrium problems. I have come upon two examples of a problem in two different Youtube videos which got me confused:
Example 1: 19% of a population shows the dominant phenotype. What is the dominant allele frequency?
The instructor in the video says that we should address 19% as a combination of both dominant homozygous and heterozygous, so:
p^2 + 2pq = 0.19
Example 2: In a given population of velociraptors that assumes Hardy-Winberg principles, brown skin is homozygous dominant, and gray skin is homozygous recessive. If the percentage of brown-skinned Velociraptors is 64%, what percentage of velociraptors are Heterozygous?
In this case, the instructor says that p^2 = 0.64.
What I don't understand is why in this case p^2 = 0.64 and not 2pq + p^2 = 0.64.
Couldn't the heterozygous velociraptors also have brown skin?
First: (Minute 17) https://youtube.com/watch?v=NS3BjKWHK1s
Second: (Minute 5:20) https://youtube.com/watch?v=IVGEusDdJGk