<prompt> Cytogenetic studies in a 70-year-old woman with chronic myelogenous leukemia CML demonstrate a t9;22 chromosomal translocation. Which of the following best explains the role of this translocation in the pathogenesis of leukemia in this patient?Altered DNA methylation statusEnhanced expression of telomerase geneExpansion of a trinucleotide repeatProtooncogene activation  <response>: Philadelphia chromosome is the best-known example of an acquired chromosomal translocation in a human cancer It is found in 95 of patients with CML. The c-abl protooncogene on chromosome 9 is translocated to chromosome 22 The c-abl gene and bcr region unite to produce a hybrid oncogene that codes for an aberrant protein with very high levels of tyrosine kinase activity, which generates mitogenic and antiapoptotic signals. 