Question

How many kinds of phenotypes would you expect in the F2 generation in a monohybrid cross, exhibiting codominance? [Delhi 2014]

Answer 1

Answer:

three kinds....

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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.