Explain the inheritance of two genes' in pea plants with two suitable examples.

Explanation

Schematic representation of dihybrid cross (two gene inheritance)

Dihybrid Phenotypic ratio= Round yellow 9: Round green 3: Wrinkled yellow 3: Wrinkled green, i.e. 9:3:3:1
`P_1`
F
`F_2` checker board
`F_2` Phenotypic ratio
Detailed Answer:
Inheritance of Two Genes
Dihybrid Cross
A cross between two parents differing in two pairs of contrasting characters.
Mendel made some dihybrid crosses e.g. Cross between pea plant with round shaped and yellow coloured seeds (RRYY) and wrinkled shaped and green coloured seeds (rryy).
On observing the F, Mendel found that the yellow and green colour segregated in a 3:1 ratio.
Round and wrinkled seed shape also seg regated in a 3:1 ratio.
Thus, the segregation of one pair of contrasting characters (Round and wrinkled shape) is independent of the segregation of another pair of contrasting character (yellow and green) colour and also that some new combinations of character appear in `F_2` generation as the alleles get randomly rearranged in the offsprings at the time of fertilization.
Dihybrid genotypic ratio: 1:2:1:2:4:2: 1:2:1
RRYY = 1, RRYy = 2, RrYY = 2, RrYy = 4, RRyy = 1, Rryy = 2, rrYY = 1, rrYy = 2, rryy = 1