Question

N a simple mendelian monohybrid cross, true-breeding tall plants are crossed with short plants, and the f1 plants, which are all tall, are allowed to self-pollinate. what fraction of the f2 generation will be both tall and heterozygous?

Answer 1

T- tall allele
t- small allele

The parental cross is true-breeding, so: TTx tt

The F1 generation will be all tall heterozygote: Tt

The F2 generation will be between 2 plants with the same genotype: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

answer: 1/2 of the plants are tall heterozygote in F2 generation.