Study the following cross and the self-pollination in $F_1$. Fill in the blank and answer the question that follows:
Parents: $RRYY \times rryy$
(Round,yellow) (Wrinkled,green)
$F_1$: $RrYy \times$ ?
(Round,yellow)
What are the combinations of characters in the $F_2$ progeny? What are their ratios?

(D) The cross represents a dihybrid cross. The $F_1$ generation is self-pollinated,so the cross is $RrYy \times RrYy$.
The combinations of characters in the $F_2$ progeny and their phenotypic ratios are:
$(i)$ Round,yellow: $9$
$(ii)$ Round,green: $3$
$(iii)$ Wrinkled,yellow: $3$
$(iv)$ Wrinkled,green: $1$
The phenotypic ratio is $9 : 3 : 3 : 1$.