what is the Philadelphia chromosome (Ph) ?
ARC: The hallmark of CML is the presence of the Philadelphia chromosome that forms as a result of a reciprocal translocation between chromosomes 9 and 22. The translocation is designated t(9;22). There are 46 chromosomes and the Philadelphia chromosome is formed when genetic materials exchange between chromosomes 9 and 22. The c-abl portion of chromosome 9 is translocated to the bcr region of chromosome 22. This results in a longer chromosome 9 called Derivative 9 and the shorter than usual Chromosome 22 also called the Philadelphia chromosome, containing the fused bcr-abl gene. The fusion gene expresses a specific mRNA, which generates a protein known as p210. The Philadelphia chromosome, bcr-abl fusion gene and the p210 protein can all be detected by techniques such as cytogenetics, fluorescence in-situ hybridisation (FISH) and Polymerase Chain Reaction (PCR) techniques and indicates a diagnosis of CML. 90% of patients have the classical Ph chromosome but 10% of patients may have cry
