In this case there is a reorganization of the genetic material in the cell. Such a reorganization may occur within a single chromosome or by exchange of material between chromosomes. Repeated copying of a normal oncogene can lead to its amplification in the chromosome and consequently to increased amounts of the oncogene product. The insertion of the myc -gene containing chromosome segment is such that it becomes located close to hyperactive genes directing the synthesis of antibody protein. As a consequence the myc -gene becomes activated.
Chromosome translocations occur in many different tumors.
Chromosome analysis can therefore be of considerable value for localization of genetic changes in the genome critical for tumor development. Figure 3 . Chromosome translocation in Burkitt's lymphoma. Segments have been exchanged between chromosomes 8 and 14 which has activated the oncogene myc . Oncogenes with point mutations have been observed in many tumors.