Final answer:
The reciprocal crossing over between chromosomes 9 and 22 produces the Philadelphia chromosome, which is responsible for chronic myelogenous leukemia (CML).
Step-by-step explanation:
The reciprocal crossing over between chromosomes 9 and 22 produces the Philadelphia chromosome, which is responsible for chronic myelogenous leukemia (CML). This translocation occurs when a segment of DNA from chromosome 9 and a segment of DNA from chromosome 22 break off and swap places. The resulting Philadelphia chromosome leads to the production of the BCR-abl fusion protein, which is an oncogenic tyrosine kinase involved in the development of CML.