Gene B controls the large size of starch grains, while another form b forms small grain size. Which of the given character will be expressed by genotypic combination Bb in Pisum ?

Options

A. Wrinkled seed
B. Round seed
C. Intermediate sized starch grains
D. Both (2) & (3)

Answer

To solve the question regarding the genotypic combination Bb in Pisum sativum (pea plant) and its effect on starch grain size, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Genes and Their Effects**:
- Gene B (dominant) controls large size starch grains.
- Gene b (recessive) controls small size starch grains.

2. **Understand the Genotypic Combination**:
- The genotypic combination Bb indicates a heterozygous condition where one allele is dominant (B) and the other is recessive (b).

3. **Determine the Dominance Relationship**:
- In typical Mendelian inheritance, the dominant allele (B) would express the trait associated with it (large starch grains) when present.
- However, in this case, the problem suggests that B and b are not exhibiting complete dominance. Instead, they may show incomplete dominance or co-dominance.

4. **Analyze the Resulting Phenotype**:
- Since both alleles (B and b) are contributing to the phenotype, the resulting starch grain size will not be purely large or small. Instead, it will be an intermediate size due to the influence of both alleles.

5. **Conclusion**:
- Therefore, the character expressed by the genotypic combination Bb in Pisum sativum will be intermediate size starch grains.

### Final Answer:
The character expressed by the genotypic combination Bb in Pisum is **intermediate size starch grains**.

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