DIHYBRID INHERITANCE  

Gregor Mendel crossed plants which differ in two pairs of contrasting characteristics e.g. seed shape (round or wrinkled seeds) and seed colour (yellow or green seeds). He crossed plants having round and yellow seeds with these having wrinkled and green seeds. The F1 seeds were having round and yellow seeds. Self-pollinating F1 plants produced the F2 plants of four (4) types

1. Round and yellow seeds : 9
2. Wrinkled and yellow seeds : 3

• Round and green seeds : 3

1. Wrinkled and green seeds : 1

This experiment resulted into Mendel’s second law of inheritance

Mendel’s second law of inheritance otherwise known as law of independent assortment of genes state that alleles of genes on different chromosomes assort independently during meiosis

Diagrammatically:

Parents’ genotypes:     RYRY        X          ryry

(Round yellow seed)     (Wrinkled green seed)

Gametes:                      RY         RYry          ry

F1:                           RYry   RYry RYry RYry   (all round yellow)

Self pollinating:

RYry      x       RYry

RY       rY        Ry       ry

Round and yellow seeds: (1), (2), (3), (4), (5),   (7), (9), (10), (13)        :  9

Wrinkled and yellow seeds: (6), (8), (14)                                :  3

Round and green seeds:  (11), (12), (15)                 :  3

Wrinkled and green seeds:  (16)                                                            :  1