Answer:
3 yellow : 1 green
Explanation:
Yellow seed allele (Y) is dominant over the green seed allele (y).
A cross between two true breeding parents is done: YY x yy
The F1 offspring would be heterozygous Yy.
If the F1 is selfed (Yy x Yy) the expected ratios for the F2 generation according to Mendel's law of segregation would be:
So 3/4 seeds of the F2 would be yellow because they have a dominant Y allele, and 1/4 would be green.
The phenotypic ratio will be 3 yellow : 1 green