Correction for my last post:

The recessive nature of Rh- blood is NOT the reason for low frequencies

Within my last post, I started the graph at F1 and it was reflecting something other than the original F1 from the self-pollination image.

This is more accurate:

Recessive nature reflected with phenotypes reflecting percentages of genes present, recessive or dominant

Being that our example begins with YY and yy

one is yellow, the other green making it 50/50 percentage wise.

The recessive nature is shown in F2 (second generation) where 25% are green which the new graph now reflects.

If the F1 example had a heterozygote Yellow (Yy), we would start with

Yy and yy

which would mean 50% yellow as well.

In that case, F2 would be the same with F3 being 5/8 and F4 being 11/16 green.

In such case, a graph would show green percentages approaching 75% which is the same as the presence of the genes regardless of phenotype in the beginning F1, the same as the graph I am using shows green approaching 50% as is the frequency of the genes in the YY and yy example using homozygotes.