Question

In tomato plants, the tall vine allele (T) is dominant to the short vine allele (t). Two tomato plants are crossed. Among the offspring plants grown from seed, 45% have tall vines and 55% have short vines. What are the most likely genotypes that you would predict for the parent plant

Answer 1

The most likely genotypes of the parents are hetero_zygous (Tt) and homo_zygous recessive (tt). It is only this combination that you can produce close to a 50/50 ratio between the dominant and recessive phenotypes.

A cross between two hetero_zygous parents will produce a phenotypic ratio of 3:1, with the dominant phenotype winning over 75% of the time.

A cross between a homo_zygous dominant parent with any other parent will produce all offspring with the dominant phenotype.

A cross between two homo_zygous recessive parents will produce all offspring with the recessive phenotype.

So only a cross between a hetero_zygous and a homo_zygous recessive parent will produce a ratio close to that of the question.