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In genetics, chromosome translocation is a phenomenon that results in unusual rearrangement of chromosomes. This includes balanced and unbalanced translocation, with two main types: reciprocal, and Robertsonian translocation. Reciprocal translocation is a chromosome abnormality caused by exchange of parts between non-homologous chromosomes. Two ...
In cancer, c-myc is often constitutively (persistently) expressed. This leads to the increased expression of many genes, some of which are involved in cell proliferation, contributing to the formation of cancer. [1] A common human translocation involving c-myc is critical to the development of most cases of Burkitt lymphoma. [2]
A chromosome translocation occurs in patients with CML. Part of chromosome 9 breaks off and attaches itself to chromosome 22, facilitating exchange of genetic material between chromosomes 9 and 22. The rearrangement of the chromosomes changes the positions and functions of certain genes, which causes uncontrolled cell growth. [4]
The chromosomal defect in the Philadelphia chromosome is a reciprocal translocation, in which parts of two chromosomes, 9 and 22, swap places. The result is that a fusion gene is created by juxtaposing the ABL1 gene on chromosome 9 (region q34) to a part of the BCR (breakpoint cluster region) gene on chromosome 22 (region q11).
The first fusion gene [1] was described in cancer cells in the early 1980s. The finding was based on the discovery in 1960 by Peter Nowell and David Hungerford in Philadelphia of a small abnormal marker chromosome in patients with chronic myeloid leukemia—the first consistent chromosome abnormality detected in a human malignancy, later designated the Philadelphia chromosome. [3]
There are 2 different types of chromosomal translocations that can occur: translocation events which relocate a proto-oncogene to a new chromosomal site that leads to higher expression; translocation events that lead to a fusion between a proto-oncogene and a 2nd gene (this creates a fusion protein with increased cancerous/oncogenic activity)
This type involves myc oncogene translocation from chromosome 8 to the Ig lambda locus on chromosome 22. This type of translocation is involved in about 5% of cases of Burkitt lympohoma. The c-myc gene found on chromosome 8 is part of the MYC family of genes that serve as regulators of cellular transcription and is associated with Burkitt lymphoma.
This results in the two daughter cells receiving an uneven chromatid. [4] Since the two resulting chromatids lack telomeres, when they replicate the BFB cycle will repeat, and will continue every subsequent cell division until those chromatids receive a telomere, usually from a different chromatid through the process of translocation. [4]