Answer:
27/64
Explanation:
The genotype of the heterozygous plant can be written as AaLlYy and the cross would be AaLlYy x AaLlYy.
If the three genes are independent, we can analyze each gene individually, obtain the proportion of offpsring with the dominant allele for each gene, and then multiply those probabilities to obtain the probability of having A_L_Y_ offspring, because the rules of probability state that the probability of two independent events occurring at the same time can be calculated as the multiplication of the probabilities of occurrence of each event.
Aa x Aa
Ll x Ll
Yy x Yy
So the total proportion of offspring with dominant phenotype for all traits will be 3/4 × 3/4 × 3/4 = 27/64