Question

Having attached ear lobes is a recessive trait in humans. If 65 out of 200 people in Population Y have attached ear lobes, what percent of Population Y is homozygous dominant?

Answer 1

Read about Castle-Hardy-Weinburg on Wikipedia.

1 = q^2 + 2pq + p^2.

In this case it tells you that the proportion homozygous recessive - represented by q^2 - is 65 out of 200. 65 divided by 200 equals 0.325.

So 0.325 = q^2. So find q. q is the square root of 0.325. So q = 0.5700877.

Plug your value for q into the equation and you have one equation with one unknown value:

1 = 0.325 + (2)(0.5700877)p + p^2.

Solve it for your unknown value.

And then square it because what you're really after is p^2. And that's your answer.