Correct option is B
The Philadelphia chromosome (Ph) is a well-known genetic abnormality associated with chronic myelogenous leukemia (CML). It results from a reciprocal translocation between chromosome 9 and chromosome 22, forming the BCR-ABL fusion gene , which leads to unregulated tyrosine kinase activity, causing excessive cell proliferation.
Now, let's analyze each statement:
Statement A: "The DNA sequence was identical in the translocation breakage and rejoining (TBR) sections in all leukemic cells in all 4 patients."
- Incorrect. While the BCR-ABL fusion gene is always present in CML, the breakpoints in the translocation can vary among patients. Different individuals tend to have slightly different translocation breakage and rejoining (TBR) sequences, making this statement incorrect.
Statement B: "The DNA sequence was identical in all leukemic cells from patient 1, but every patient had a different TBR sequence."
- Correct. Within a single patient, all leukemic cells share the same translocation pattern. However, across different individuals, the translocation breakpoints differ, which is consistent with known variations in CML patients.
Statement C: "All patients have translocations between long arms of chromosomes 9 and 22."
- Correct. The Philadelphia chromosome is formed due to a translocation between the long arms of chromosome 9 and chromosome 22. This leads to the creation of the BCR-ABL oncogene, which is responsible for uncontrolled cell division in leukemia.
Statement D: "All patients have translocations between the long arm of chromosome 9 and the short arm of chromosome 22."
- Incorrect. While the translocation does involve chromosome 9 and chromosome 22, the standard description in cytogenetics refers to the involvement of the long arms of both chromosomes rather than the short arm of chromosome 22. The BCR gene on chromosome 22 and ABL gene on chromosome 9 recombine in their long-arm regions.
Since statements B and C are correct, the correct answer is option 2 (B and C).
