The yellow leaf was not exposed to the sun so it can't produce sugar.
Explanation:
The yellow region of the leaf didn't produce sugar because it wasn't exposed to sunlight. Part of the leaf was exposed to the sun, thus this leaf produced sugar, while the yellow part of the leaf did not because it was not exposed to the sunlight.
No, they aren't always visible. It depends if its heterozygous or homozygous.
Homo- 2 of the same gene. Ex. RR or rr
Heter- both genes are different. Ex Rr
