Mendel's earlier experiments in garden pea (Pisum sativum) were mono hybrid crosses. A cross involving contrasting expression of one trait is transferred to as monohybrid cross. For example, in order to learn inheritance of plant height, a tall pea plant was crossed with a dwarf one; all other traits were ignored.
Inheritance of two pairs of alleles through a number of generations was studied by Mendel through dihybrid crosses. In one experiment Mendel crossed a round green’ with a wrinkled yellow. The F1 individuals, called dihybrid, were all round yellow. Two members of the F1 were crossed to raise the F2 . The result was 315 round yellow + 108 round green + 101 wrinkled yellow + 32 wrinkled green. This observed figures closely approximated a 9:3:3:1 ratio.
Monohybrid vs Dihybrid
It is a cross between two pure organisms in order to study the inheritance of a single pair of alleles.
It is a cross between two pure organisms of a species in order to study the inheritance of two pairs of alleles belonging to two different characters.
It produces a phenotypic monohybrid ratio of 3:1 in F2 generation.
It produces a phenotypic dihybrid ratio of 9:3:3:1 in F2 generation.
It produces genotypic ratio of 1:2:1 in F2.
It produces genotypic ratio of 1:2:1:2:4:2:1:2:1
Test cross ratio - 1:1
Test cross ratio -1:1:1:1