Select the incorrect pair.

Options

A. Incomplete dominance - Dog flower
B. Pleiotropy - Phenylketonuria
C. Female heterogametic - Grasshopper
D. Klinefelter's syndrome - XXY

Answer

To solve the question of identifying the incorrect pair, we will analyze each of the given options step by step.

### Step-by-Step Solution:

1. **Option A: Incomplete dominance and dog flower (Antirrhinum)**
- Incomplete dominance occurs when the phenotype of the heterozygote is intermediate between the phenotypes of the two homozygotes.
- The dog flower (Antirrhinum) is a classic example of incomplete dominance, where crossing red and white flowers results in pink flowers.
- **Conclusion:** This pair is correct.

2. **Option B: Pleiotropy and phenylketonuria (PKU)**
- Pleiotropy refers to a situation where one gene influences multiple phenotypic traits.
- Phenylketonuria is a genetic disorder caused by a mutation in a single gene that affects multiple metabolic pathways related to phenylalanine metabolism.
- **Conclusion:** This pair is correct.

3. **Option C: Female heterogametic grasshopper**
- In grasshoppers, the males are heterogametic, meaning they have two different sex chromosomes (X and Y), while females are homogametic, having two of the same sex chromosome (XX).
- Therefore, the statement that females are heterogametic is incorrect.
- **Conclusion:** This pair is incorrect.

4. **Option D: Klinefelter syndrome and XXY**
- Klinefelter syndrome is a genetic condition that occurs in males who have an extra X chromosome, resulting in the XXY chromosomal pattern.
- This is a well-established fact in genetics.
- **Conclusion:** This pair is correct.

### Final Answer:
The incorrect pair is **Option C: Female heterogametic grasshopper**.

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