Question

In a cross between a pure tall pea plant with green pod and a pure short plant with yellow pod, how many short plants out of 16 would you expect in the F2 generation?
A. 3
B. 4
C. 9
D. 1

Answer 1

Hint: Gregor Johann Mendel first conducted the experiments on pea plants and observed the transmission of genes from one generation to the other. He considered inheritance of one gene in monohybrid cross and inheritance of two genes in a dihybrid cross.

Complete answer: A dihybrid cross is a cross between two plants that are identical hybrids for two traits. The two plants are heterozygous for two traits. A pure pea plant with green pods is homozygous for dominant traits and a pure short plant with yellow pods is homozygous for recessive traits. In the F1 generation, all heterozygous plants are produced and in the F2 generation, plants with the ratio of 9:3:3:1 are produced. When the cross is made between a pure tall pea plant and a pure short pea plant, all tall green plants are produced in the F1 generation and 16 plants are produced in the F2 generation. Out of 16 plants, 9 are tall green, 3 are tall yellow, 3 are dwarf green and 1 is dwarf yellow. Tall and green pods are the dominant traits and small and yellow are the recessive traits. Observing the ratio of dihybrid cross i.e. 9:3:3:1 ratio, 9 plants have both dominant features, 3 have first dominant and second recessive features, 3 have first recessive and second dominant feature and 1 have both recessive features. Out of 16 plants produced in the F1 generation, 12 are tall plants and 4 are short plants.
Hence, option B is the correct answer.

Note: In genetics, three laws proposed by Gregor Mendel plays an important role: They are
i. Law of dominance
ii. Law of segregation
iii. Law of independent assortment.