Question

Work out separate monohybrid crosses up to F2 generation between two pea plants and two Antirrhinum plants, both having contrasting traits with respect to the colour of the flower. Comment on the patterns of inheritance in the crosses carried out in such two cases.

Hint:

Remember: A monohybrid cross involves the inheritance of a single trait, and the ratio observed in the offspring follows Mendel's laws of inheritance.

Answer 1

Monohybrid Cross in Pea Plants (Mendel's experiment):
For pea plants, let us assume that the contrasting traits are: Purple flower (P) is dominant, and White flower (p) is recessive.
- Parental Cross (P generation):
- \text{Purple flower} (P) x \text{White flower} (p)
\[ \text{F1 generation:} Pp \text{ (All purple-flowered offspring)} \] - F1 x F1 Cross:
- \[ Pp \times Pp \quad \text{(F1 x F1)} \] - The offspring (F2 generation) will have the following genotypic and phenotypic ratio:
- Genotypic ratio: 1 PP : 2 Pp : 1 pp
- Phenotypic ratio: 3 Purple : 1 White

Monohybrid Cross in Antirrhinum Plants (Snapdragon):
For Antirrhinum plants, let us assume that the contrasting traits are: Red flower (R) is dominant, and White flower (r) is recessive.
- Parental Cross (P generation):
- \text{Red flower} (RR) x \text{White flower} (rr)
\[ \text{F1 generation:} Rr \text{ (All red-flowered offspring)} \] - F1 x F1 Cross:
- \[ Rr \times Rr \quad \text{(F1 x F1)} \] - The offspring (F2 generation) will have the following genotypic and phenotypic ratio:
- Genotypic ratio: 1 RR : 2 Rr : 1 rr
- Phenotypic ratio: 3 Red : 1 White

Conclusion:
- In both crosses, the dominant trait appears in the F1 generation.
- In the F2 generation, both the dominant and recessive traits are visible.
- The Mendelian inheritance pattern follows a 3:1 phenotypic ratio and a 1:2:1 genotypic ratio in both cases.