Question

When two plants, both tall, were crossed, they produced some offspring that were dwarves. Assuming that the height of the plant is controlled by a single gene and the allele for the tall plant is dominant, what is the genotype of the parents?

Answer 1

T- tall allele
t- dwarf allele

This cross needs to be between 2 plants with the same genotype, like Tt xTt

In this cross it would result in:
1/4 of the plants being tall homozygote- TT
2/4 of the plants being tall heterozygote- Tt
1/4 of the plants being dwarfs homozygote- tt