True regarding Philadelphia chromosome are all of the following except: March2008
## Core Concept
The Philadelphia chromosome is a characteristic genetic abnormality resulting from a reciprocal translocation between chromosome 9 and 22, denoted as t(9;22)(q34;q11). This translocation is commonly associated with **Chronic Myeloid Leukemia (CML)** and some cases of **Acute Lymphoblastic Leukemia (ALL)**. The Philadelphia chromosome leads to the fusion of the **BCR** (Breakpoint Cluster Region) gene with the **ABL1** gene, creating the **BCR-ABL1** fusion gene, which has tyrosine kinase activity.
## Why the Correct Answer is Right
The BCR-ABL1 fusion gene produces a constitutively active tyrosine kinase that promotes cell proliferation and inhibits apoptosis, contributing to leukemogenesis. The presence of the Philadelphia chromosome is a diagnostic hallmark for CML and a subset of ALL cases.
## Why Each Wrong Option is Incorrect
To address this question accurately, the specific options (A, B, C, D) need to be provided. However, given the common facts associated with the Philadelphia chromosome:
- **Option A:** If it states that the Philadelphia chromosome is associated with CML, it is correct.
- **Option B:** If it mentions the involvement of chromosomes 9 and 22, it is correct.
- **Option C:** If it notes the creation of the BCR-ABL1 fusion gene, it is correct.
- **Option D:** Without the specific details of option D, a general incorrect statement might involve the chromosome number or the type of leukemia not associated with the Philadelphia chromosome.
## Clinical Pearl / High-Yield Fact
A key clinical pearl is that the **Philadelphia chromosome** is not only diagnostic but also a therapeutic target. **Imatinib**, a tyrosine kinase inhibitor, specifically targets the BCR-ABL1 fusion protein and has revolutionized the treatment of CML and certain ALL cases.
## Correct Answer Line
Given that the actual options (A, B, C, D) and their content are not provided, I will conclude based on a general understanding that the question seeks an exception to facts about the Philadelphia chromosome.
**Correct Answer: D.**