Two pure-breeding strains of summer squash producing yellow fruit, Y₁ and Y₂, are each crossed to a pure-breeding strain of summer squash producing green fruit, G₁, and to one another. The following results are obtained:

If the F₁ of Crosses I and II are mated, predict the phenotype ratio of the progeny. 

Verified step by step guidance

1. Identify the genotypes of the parental strains based on the F1 and F2 results.
2. For Cross I, since all F1 are yellow, Y1 is likely dominant over G1. Assume Y1 is YY and G1 is gg.
3. For Cross II, since all F1 are green, Y2 is likely recessive to G1. Assume Y2 is yy and G1 is GG.
4. Cross the F1 from Cross I (Yg) with the F1 from Cross II (Gg) to predict the F2 phenotypes.
5. Use a Punnett square to determine the phenotype ratio of the progeny from the F1 cross (Yg x Gg).