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Fusion gene
 
 
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A fusion gene is a hybrid gene formed from two previously separate genes. It can occur as the result of a translocation
Chromosomal translocation

In genetics, a chromosome translocation is a chromosome abnormality caused by rearrangement of parts between nonhomologous chromosomes. A fusion gene may be created when the translocation joins two otherwise separated genes, an event which is common in cancer....
, interstitial deletion, or chromosomal inversion
Chromosomal inversion

An inversion is a chromosome rearrangement in which a segment of a chromosome is reversed end to end. An inversion occurs when a single chromosome undergoes breakage and rearrangement within itself....
. Often, fusion genes are oncogene
Oncogene

An oncogene is a gene that, when mutated or expressed at high levels, helps turn a normal cell into a cancer cell.Many cells normally undergo a programmed form of death ....
s; examples include BCR-ABL
Philadelphia chromosome

Philadelphia chromosome or Philadelphia translocation is a specific chromosome abnormality that is associated with chronic myelogenous leukemia ....
, TEL-AML1 (ALL
Acute lymphoblastic leukemia

Acute lymphoblastic leukemia , is a form of leukemia, or hematological malignancy characterized by excess lymphoblasts.Malignant, immature lymphoblasts continuously multiply and are overproduced in the bone marrow....
 with t(12 ; 21)), AML1-ETO (M2 AML with t(8 ; 21)) and TMPRSS2-ERG with an interstitial deletion on chromosome 21, often occuring in prostate cancer. Most fusion genes are found from hematological cancers, sarcomas and prostate cancer.

Oncogenic fusion genes may lead to a gene product with a new or different function from the two fusion partners.






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A fusion gene is a hybrid gene formed from two previously separate genes. It can occur as the result of a translocation
Chromosomal translocation

In genetics, a chromosome translocation is a chromosome abnormality caused by rearrangement of parts between nonhomologous chromosomes. A fusion gene may be created when the translocation joins two otherwise separated genes, an event which is common in cancer....
, interstitial deletion, or chromosomal inversion
Chromosomal inversion

An inversion is a chromosome rearrangement in which a segment of a chromosome is reversed end to end. An inversion occurs when a single chromosome undergoes breakage and rearrangement within itself....
. Often, fusion genes are oncogene
Oncogene

An oncogene is a gene that, when mutated or expressed at high levels, helps turn a normal cell into a cancer cell.Many cells normally undergo a programmed form of death ....
s; examples include BCR-ABL
Philadelphia chromosome

Philadelphia chromosome or Philadelphia translocation is a specific chromosome abnormality that is associated with chronic myelogenous leukemia ....
, TEL-AML1 (ALL
Acute lymphoblastic leukemia

Acute lymphoblastic leukemia , is a form of leukemia, or hematological malignancy characterized by excess lymphoblasts.Malignant, immature lymphoblasts continuously multiply and are overproduced in the bone marrow....
 with t(12 ; 21)), AML1-ETO (M2 AML with t(8 ; 21)) and TMPRSS2-ERG with an interstitial deletion on chromosome 21, often occuring in prostate cancer. Most fusion genes are found from hematological cancers, sarcomas and prostate cancer.

Oncogenic fusion genes may lead to a gene product with a new or different function from the two fusion partners. Alternatively, a proto-oncogene is fused to a strong promoter, and thereby the oncogenic function is set to function by an upregulation caused by the strong promoter of the upstream fusion partner. The latter is common in lymphomas, where oncogenes are juxtaposed to the promoters of the immunoglobulin genes.

Presence of certain chromosomal aberrations and their resulting fusion genes is commonly used within cancer diagnostics in order to set a precise diagnosis. In routine diagnostic laboratories the following methods are most commonly used: chromosome banding analysis, fluorescence in situ hybridisation, and RT-PCR. These methods all have their distinct shortcomings due to the very complex nature of cancer genomes. Recent developments such as high-throughput sequencing and custom-designed DNA microarrays bear promise of introduction of more efficient methods.

Biologists may also deliberately create fusion genes for research purposes. For example, by creating a fusion gene of a protein of interest and green fluorescent protein
Green fluorescent protein

The green fluorescent protein is composed of 238 amino acids , originally isolated from the jellyfish Aequorea victoria that fluorescence green when exposed to blue light....
, the protein of interest may be observed in cells
Cell (biology)

The cell is the structural and functional unit of all known Life organisms. It is the smallest unit of an organism that is classified as living, and is often called the building bricks of life....
 or tissue
Biological tissue

Tissue is a cellular organizational level intermediate between cells and a complete organism. Hence, a tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function....
 using fluorescence microscopy
Microscopy

Microscopy is the technical field of using microscopes to view samples or objects. There are three well-known branches of microscopy, optical microscopy, electron microscopy and scanning probe microscopy....
. The protein synthesized when a fusion gene is expressed
Gene expression

Gene expression is the process by which inheritable information from a gene, such as the DNA sequence, is made into a functional gene product, such as protein or RNA....
 is called a fusion protein
Fusion protein

Fusion proteins, AKA chimeric proteins, are proteins created through the joining of two or more genes which originally coded for separate proteins....
.