Mendelian Genetics Questions

A common test to find the genotype of a hybrid is by:

In pea plants, yellow seeds are dominant to green. If a heterozygous yellow seeded plant is crossed with a green seeded plant, what ratio of yellow and green seeded plants would you expect in $F_1$ generation?

$F_2$ generation in a Mendelian cross showed that both genotypic and phenotypic ratios are same as $1:2:1$. It represents a case of: