Reciprocal translocation in CML
(Chronic Myologenous Lukemia):
the Philadelphia
Chromosome
Standard Chromosomes 9 &
22 are shown at left: they are subject to breakage at
the abi
and bcr loci, respectively. The so-called Philadelphia Chromosome is
detectable cytologically as an extra G-group chromosome due to
the apparent shortening of the F-group Chromosome 22 by a reciprocal exchange
with chromosome 9. Juxtaposition of the abl and
bcr loci
interferes with cancer suppressor genes, and results in a
specific form of Leukemia. Philadelphia
Chromosome was one of the first genetic conditions
shown to be associated with cancer.