Why is the frequency of A and a in the F2 generation (0.5 for A and 0.5 for a)?

Question

In humans, the hypothetical disease Allomentia, is carried on the allele "a", which is recessive to "A" for the normal condition.

(Figure 1 is AA and aa)

(Figure 2 is Aa and Aa)

Answer 1

its 25% . Cause you would need a aa to get it and only 25% of chances could happen in that form in a punnett square.

Answer 2

So am I to assume from your "figure 1" and "figure 2" that the

Po (parental) genotypes were AA X aa?

If so, the F1 generation will be 100% heterozygous Aa

___a___ a_

A  | Aa   Aa

A  | Aa   Aa

If the F1 cross is Aa X Aa, then . . .

___A ___a_

A  |  AA   Aa

a   |  Aa   aa

0.5 Aa, 0.25 AA, 0.25 aa

Does that help?

Answer 3

idk.

ask a rocket scientist :D

Answer 4

There are 2 alleles segregating and their total adds up to 1.00 or 100%.  50% or 0.5 for each in either case.

The frequency of "a" is the total occurences of "a" divided by the total number of A's and a's (A+a) in the F2's.  

Same with "A"

For this problem, you're not considering whether individuals have Allomentia or not, you're strictly just looking at the frequency of occurence of a given allele in the total population.