Question

What phenotypic and genotypic ratios are expected in F2 generation when monohybrid and dihybrid crosses are made.

Answer 1

Phenotypic-F2 generation 3:1

Genotypic-F2 generation 1:2:1

For mono hybrid

Phenotypic F2 gene. 9:3:3:1

Genotypic F2 gene. 1:2:1:2:4:2:1:2:1

For dihybrid

Hope it helps.....

Answer 2

both the genes express themselves equally in the heterozygous condition. Therefore, three different kinds of phenotypes would be seen in the F2 generation in a monohybrid cross.  

Example: Colour inheritance in snapdragon.

Red flower: RR; White flower: rr

F1 generation: RR * rr

                             ↓

                            Rr

F2 generation: Rr * Rr

                            ↓

                    RR Rr Rr rr

Three phenotypes are seen i.e. Red (RR), pink (Rr) and white (rr).

According to the law of dominance, the phenotype of Rr should be red since R is dominant over r. But Snapdragon does not follow Mendelian inheritance. R is not able to completely express itself over r. This results in a third phenotype (here, pink).

Therefore, three phenotypes are seen in F2 generation in a monohybrid cross.