Re: What is the Philadelphia Chromosome?

Dear Amy,

The Philadelphia Chromosome is a characteristic cytogenetic abnormality 
associated with leukemia (CML - chronic myeloid leukemia - and some acute 
cases) as you have found in your literature. 

The Philadelphia chromosome results from a reciprocal translocation between 
chromosomes 9 and 22 [t(9;22)(q34;q11)]. The molecular changes involve the 
translocation of the abl oncogene on chromosome 9 to the major breakpoint 
cluster region on chromosome 22, with production of the bcr/abl hybrid 
gene. 

In CML, the Philadelphia chromosome is present in all cells of the myeloid 
lineage, including neutrophils, erythroblasts, megakaryocytes, monocytes, 
eosinophils and basophils.