Theoretically a normal phenotype is expressed when a particular substrate transform in to product but in which of following conditon phenotype may be affected-

Options

A. When the modified allele produce normal enzyme
B. When the modified allele produce a non functional enzyme
C. When the unmodified allele produce no enzyme
D. All the above

Answer

To solve the question regarding the conditions under which a phenotype may be affected when a substrate is transformed into a product, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Normal Phenotype**:
- A normal phenotype is expressed when a specific substrate is converted into a product through the action of enzymes. These enzymes are typically produced by genes.

2. **Role of Alleles**:
- Alleles are different versions of a gene. A modified allele can lead to changes in the enzyme produced, which in turn can affect the phenotype.

3. **Analyzing the Conditions**:
- **Condition 1**: If a modified allele produces a normal enzyme, the phenotype remains unaffected. This means that the substrate is still converted into the product efficiently.
- **Condition 2**: If a modified allele produces a non-functional enzyme, the conversion of the substrate into the product is impaired. This will lead to a change in the phenotype because the necessary product is not being formed.
- **Condition 3**: If an unmodified allele produces no enzyme, this condition is not possible because an unmodified allele typically produces a normal enzyme. Thus, the phenotype would not be affected in this case.

4. **Conclusion**:
- Based on the analysis, the only condition that would lead to an affected phenotype is when the modified allele produces a non-functional enzyme. Therefore, the correct answer is that the phenotype may be affected when the modified allele produces a non-functional enzyme.

### Final Answer:
- The phenotype may be affected when the modified allele produces a non-functional enzyme.