Question

Write differences between Monohybrid and Dihybrid cross (on the basis of phenotypic ratio).

Answer 1

Monohybrid cross:

1. It is a cross between two organisms of the same species with the inheritance of a single pair of characters or traits. (e.g. TT x tt)
2. Example: Crossing between a homozygous tall and a homozygous dwarf pea plant.
3. So, It results in a phenotypic ratio of 3:1.(3 tall plants : 1 dwarf plant)

Dihybrid cross:

1. It is a cross between two organisms of the same species with the inheritance of two pairs of traits of two characters. (e.g. RRYY x rryy)
2. Example: Crossing between a pea plant with two contrasting characters- Round and wrinkled (seed shape), Yellow and green (seed colour).
3. It results in a phenotypic ratio of 9:3:3:1.( 9 yellow-round seeds : 3 green-round seeds : 3 yellow-wrinkled seeds : 1 green wrinkled seeds)

	Monohybrid cross	Dihybrid cross
Phenotypic ratio	3:1	9:3:3:1