They provide information on shared ancestry and evolutionary relationships.
There's a bunch of examples.
For example, hairlines. A widow's peak is a dominant trait over a straigh hairline.
Or dominant hand type. Right hands are dominated over left hands.
Or hair types. Curly hair dominates straight hair.
If you google it, you'll get a lot more examples.
The answer to the question is that it is
G=Green....because your starting plant is heterozygous it must be Gg
g = yellow ....because yellow is recessive, it must be gg
Gg x gg
Do a Punnet Square and you get
Gg (2)
gg (2)
So half of your plants will be green (but heterozygous) and half will be yellow (homozygous)
