Can someone PLEASE explain how this makes sense The inputted

Can someone PLEASE explain how this makes sense. The inputted genotype frequencies are NOT THE SAME as the ones calculated for in the second part. Why couldnt he just use F(AA)=p^2 TO BEGIN WITH? Then it would have returned ACCURATE genotype frequencies. PLEASE HELP I AM DESPERATE.

LET ME REITERATE MY QUESTION

f(aa)= 200/1000 = .2

f(aa)=q^2 =.2

so q= .477

HOW DOES THIS RECONSILE????

Guppies (Poecillia reticulata) are small, brightly colored fish that are common in freshwater streams in Trinidad. Imagine that the coloration is controlled by two alleles at a given gene. On a sampling trip, a young ecologist collects the following: 200 Brown guppies (AA) 600 Red guppies (Aa) 200 Yellow guppies (aa) Assuming HW equilibrium, calculate the allele & genotype frequencies of the population of guppies. 0.5 0.5 (0.5) fAA) a p 0.25 2 (0.5 0.5) 0.50 faa) q? 0.25

Solution

As per the Hardy Weinberg Equilibrium, to find out the allelic frequency,you have to consider the homozygous allelic frequency as well as half the the heterozygous frequency as it contains the allele under consideration as well.

So, f(a) = 200 /1000 + 1/2 (600/1000)

=0.2 +1/2 0.6

= 0.5 ans

f(aa) = (0.5)² = 0.25 ans