Here let me help you, DNA influences physical traits by changing how you look, sound, and function. Your parents transfer their genes into you which means you are left with characteristics of there body, such as having your father's nose. Hope this helped.
YY and Yy would result in a plant with yellow seeds. This is because Y is dominant and yellow seeds would show with a dominant homozygous and a heterozygous. It can't be yy because that would be homozygous recessive
