Question

Green seed pods are dominant to yellow and tall plants are dominant to short. If two plants are homozygous for their green seed pods and are short are crossed, what percentage of the plants would have green seed pods? (if the answer is 5, write it as 5% or in fraction form).

Please help.

Answer 1

100%

Step-by-step explanation:

This is a cross involving two different genes; one coding for seed pod color and the other for height in a plant. The allele for green seed pods (G) is dominant over the allele for yellow seed pod (g) in the first gene while the allele for tallness (T) is dominant over the allele for shortness (t) in the second gene.

According to the question, the two crossed plants are homozygous for their green seed pods and are short. Being homozygous for the green pod means that the parent plant will have a GG genotype for the first gene. A short plant exhibits the recessive trait, hence, will possess an homozygous recessive genotype i.e. tt. Therefore, the genotype of both parents crossed is: GGtt.

Each parent will undergo meiosis to produce gametes with the following allelic combinations: Gt, Gt, Gt and Gt. Using these gametes in a punnet square (see attached image), 16 possible offsprings will be produced and all offsprings will have the genotype: GGtt.

A GGtt offspring will phenotypically possess green seed pods and short traits. Since all the offsprings possess this green seed pod trait, hence, 100% of the offsprings have green seed pods