allele frequency of a population

Answer: Fr(white) = fr(bb) = 0.25, so fr(b) = sqrt(0.25) = 0.5; therefore, fr(B) = 1-0.5 = 0.5.

First, you should always try to find the frequency of q^2 (homozygous recessive genotype) if given enough information. In this case, you are indeed given enough information since there can only be 25 individuals expressing the recessive phenotype and therefore genotype (if there was a dominant allele present, the recessive trait would not be expressed). So, divide 25/100 to find the frequency of that homozygous recessive genotype in the population.

Now, you can use this information to find all of the other frequencies, so to find q (frequency of recessive allele), find the square root of your q^2 value.

Plug in q to the equation p+q=1 and solve for p in order to obtain the frequency of the dominant allele within the population.

Now that you've found p, square that value to find p^2 (the frequency of the homozygous dominant genotype within the population...

You only have one thing left to do, find the frequency of the heterozygous genotype.
Plug in p^2 and q^2 values into the equation p^2+2pq+q^2=1 and solve for 2pq. (All you've got to do is add p^2 and q^2 and subtract that from 1 to find the frequency of the heterozygous genotype...

This is a basic explanation of how to compute these values. Sorry I couldn't give you the actual values, as I don't have a calculator handy.

It is important to know basic genetics terms in order to be able to understand this concept.

A population has evolved if there is a significant difference between the initial allele frequencies of a population and the final allele frequencies of a population. 

thanks so much!