Question

The environment has changed and the frequency of the p allele has gone down, what will this do to the q allele? Cause it also to go down The q allele will remain the same The q allele will go down then up The q allele will go up.

Answer 1

The answer is The q allele will go up.

Answer 2

The answer is The q allele will go up.

Let's assume that the population is in the Hardy-Weinberg equilibrium and there are only two alleles of some gene. The Hardy-Weinberg principle can be expressed as p + q = 1 where p is the frequency of the p allele and q the frequency of q allele.
Let initial frequencies be:
p = 0.6
q = 0.4
p + q = 1
0.6 + 0.4 = 1
Now, after the environmental change, the frequency of the p allele has gone down, for example p = 0.3
So, p goes from 0.6 to 0.3.

The frequency of the q allele can be calculate using Hardy-Weinberg principle:
p + q = 1
q = 1 - p
q = 1 - 0.3
q = 0.7

Thus, q goes from 0.4 to 0.7.