Hey guys it's Breanna, I am going to be
explaining how selection has an effect
on the Hardy-Weinberg equilibrium using an
example with white, gray, and black wolves.
So the white have a homozygous A
genotype. The gray wolves have a
heterozygous AB genotype and the black
wolves have a homozygous A genotype. And
here are the numbers of each of the
individuals and using these numbers we
can find out the frequency of each
individual allele. And we use p to find that
out. So the frequency of the A allele, we
would take total number of heterozygous (homozygous*)
A over the total amount, which is 100, plus half of the heterozygous
individuals so 46 times 0.5 over the
total amount of individuals again
you would add those and you would get
0.61. Same thing for q. To find the
frequency of the B allele you would take
homozygous B individuals over the
total so, 16 over a hundred, plus same
thing, heterozygous individuals times 0.5
over the total you would get 0.39.
And then using p and q,  you can find the
genotype of each, the frequency of each
genotype. So for the white wolves, P
squared, that would be 0.371 (0.3721*)
heterozygous individuals, which would be
the grey wolves, have 2pq, so two times
p times q is 0.4758. Then the homozygous B
individuals, so the black wolves, would
have 0.1521 and you do that squaring
the q. And then for the fitness, in this
situation you can see that it is going
towards the black individuals. This is a
situation where, let's say like global
warming hit this area where they live in
this snowy environment, and the white
wolves no longer have the coverage that
they used, to the camouflage that they
used to, and now the black wolves are
hiding in, or yeah hiding better and
able to escape predators so they have a
higher fitness now. So the unadjusted
survivors, you get this by multiplying
the individual frequency times the
fitness of each one. So you get those
numbers. So when you get the unadjusted
survivors, the numbers of the unadjusted
survivors, you add them up to get the
average fitness, which is up here, and
then once you get the average fitness,
you can take each of these numbers of
the unadjusted survivors, put them over
the average fitness to get the selection
after frequency (frequency after selection*), which should always
equal one. Once you get these numbers, you
can put them in a genotypic array using
this genotypic array, you can find
the frequency of each individual allele
after selection. So using the homozygous
A and heterozygous AB times 0.5, you add
those and you get 0.549, and then same
thing with B, you get 0.451. Using
these numbers, we can plug them back into
the Hardy-Weinberg equation again and
get the frequency of each genotype after
selection. As you can see, the frequency
of each genotype is moving towards the
black wolves, as it will continue to do
in the future.
