The genotype of a green-stemmed tomato plant is denoted as $GG$ and that of a purple-stemmed tomato plant as $gg$. When these two are crossed:
$(i)$ What colour of stem would you expect in their $F_1$ progeny?
$(ii)$ Give the percentage of purple-stemmed plants if $F_1$ plants are self-pollinated.
$(iii)$ In what ratio would you find the genotypes $GG$ and $Gg$ in the $F_2$ progeny?

(A) $(i)$ Since green $(G)$ is dominant over purple $(g)$,all $F_1$ progeny will have the genotype $Gg$ and will be green-stemmed.
$(ii)$ When $F_1$ $(Gg)$ plants are self-pollinated,the $F_2$ generation results in the ratio $1GG : 2Gg : 1gg$. The purple-stemmed plants $(gg)$ represent $1$ out of $4$ plants,which is $25\%$.
$(iii)$ In the $F_2$ progeny,the ratio of genotypes $GG$ to $Gg$ is $1:2$.