Chromosomal translocation

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Chromosomal translocation

In genetics

Genetics

Genetics , a discipline of biology, is the science of heredity and Genetic variation in living organisms. The fact that living things inherit traits from their parents has been used since prehistoric times to improve crop plants and animals through selective breeding....
, a chromosome translocation is a chromosome abnormality caused by rearrangement of parts between nonhomologous chromosomes. A fusion gene

Fusion gene

A fusion gene is a hybrid gene formed from two previously separate genes. It can occur as the result of a Chromosomal translocation, interstitial deletion, or chromosomal inversion....
may be created when the translocation joins two otherwise separated genes, an event which is common in cancer

Cancer

Cancer is a class of diseases in which a group of cell display uncontrolled growth , invasion , and sometimes metastasis . These three malignant properties of cancers differentiate them from benign tumors, which are self-limited, do not invade or metastasize....
.

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Reciprocal (non-Robertsonian) translocations

Reciprocal translocations are usually an exchange of material between nonhomologous chromosomes. They are found in about 1 in 625 human newborns. Such translocations are usually harmless and may be found through prenatal diagnosis

Prenatal diagnosis

Prenatal testing is testing for diseases or conditions in a fetus or embryo before it is born. The aim is to detect birth defects such as neural tube defects, Down syndrome, chromosome abnormalities, genetic diseases and other conditions....
. However, carriers of balanced reciprocal translocations have increased risks of creating gametes with unbalanced chromosome translocations leading to miscarriages or children with abnormalities. Genetic counseling

Genetic counseling

Genetic counseling is the process by which patients or relatives, at risk of an inherited disorder, are advised of the consequences and nature of the disorder, the probability of developing or transmitting it, and the options open to them in management and family planning in order to prevent, avoid or ameliorate it....
and genetic testing

Genetic testing

Genetic testing allows the Genetics diagnosis of vulnerabilities to inherit diseases, and can also be used to determine a person's ancestry. Normally, every person carries two copies of every gene, one inherited from their mother, one inherited from their father....
is often offered to families that may carry a translocation.

Robertsonian translocations

This type of rearrangement involves two acrocentric chromosomes that fuse near the centromere

Centromere

A centromere is a region of DNA typically found near the middle of a chromosome where two sister chromatids come in contact. It is involved in cell division as the point of mitotic spindle....
region with loss of the short arms. The resulting karyotype

Karyotype

A karyotype is the characteristic chromosome complement of a eukaryote species. The preparation and study of karyotypes is part of cytogenetics....
in humans leaves only 45 chromosomes since two chromosomes have fused together. Robertsonian translocation

Robertsonian translocation

Robertsonian translocation is a common form of chromosomal rearrangement that occurs in the five Centromere#Acrocentric human chromosome pairs, namely 13, 14, 15, 21, and 22....
s have been seen involving all combinations of acrocentric chromosomes. The most common translocation in human involves chromosomes 13

Chromosome 13 (human)

Chromosome 13 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 13 spans about 113 million base pairs and represents between 3.5 and 4 % of the total DNA in cell ....
and 14

Chromosome 14 (human)

Chromosome 14 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 14 spans about 87 million base pairs and represents between 3 and 3.5% of the total DNA in cell ....
and is seen in about 0.97 / 1000 newborns. Like other translocations, carriers of Robertsonian translocations are phenotypically normal, but there is a risk of unbalanced gametes which lead to miscarriages or abnormal offspring. For example, carriers of Robertsonian translocations involving chromosome 21

Chromosome 21 (human)

Chromosome 21 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. The trisomy of the 21st chromosome causes Down Syndrome....
have a higher chance to have a child with Down syndrome

Down syndrome

Down syndrome, Down's syndrome, or trisomy 21 is a chromosomal disorder caused by the presence of all or part of an extra chromosome 21 ....
.

Some human diseases caused by translocations are:

Cancer
Cancer

Cancer is a class of diseases in which a group of cell display uncontrolled growth , invasion , and sometimes metastasis . These three malignant properties of cancers differentiate them from benign tumors, which are self-limited, do not invade or metastasize....
: several forms of cancer are caused by translocations; this has been described mainly in leukemia
Leukemia

Leukemia is a cancer of the blood or bone marrow and is characterized by an abnormal proliferation of blood Cell , usually white blood cells ....
(acute myelogenous leukemia and chronic myelogenous leukemia
Chronic myelogenous leukemia

Chronic myelogenous leukemia , also known as chronic granulocytic leukemia , is a form of leukemia characterized by the increased and unregulated growth of predominantly myeloid cells in the bone marrow and the accumulation of these cells in the blood....
).
Infertility
Infertility

Infertility primarily refers to the biological inability of a person to contribute to fertilization. Infertility may also refer to the state of a woman who is unable to carry a pregnancy to full term....
: one of the would-be parents carries a balanced translocation, where the parent is asymptomatic but conceived fetuses are not viable.
Down syndrome
Down syndrome

Down syndrome, Down's syndrome, or trisomy 21 is a chromosomal disorder caused by the presence of all or part of an extra chromosome 21 ....
is caused in a minority (5% or less) of cases by a Robertsonian translocation of about a third of chromosome 21
Chromosome 21 (human)

Chromosome 21 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. The trisomy of the 21st chromosome causes Down Syndrome....
onto chromosome 14
Chromosome 14 (human)

Chromosome 14 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 14 spans about 87 million base pairs and represents between 3 and 3.5% of the total DNA in cell ....
.

By chromosome

Denotation

The International System for Human Cytogenetic Nomenclature (ISCN) is used to denote a translocation between chromosome

Chromosome

A chromosome is an organized structure of DNA and protein that is found in Cell . A chromosome is a single piece of DNA that contains many genes, regulatory sequence and other genetic sequence....
A and chromosome B. The information in the second set of parentheses, when given, gives the precise location within the chromosome for chromosomes A and B respectively—with p indicating the short arm of the chromosome, q indicating the long arm, and the numbers after p or q refers to regions, bands and subbands seen when staining the chromosome with a staining dye. See also the definition of a genetic locus

Locus (genetics)

In the fields of genetics and evolutionary computation, a locus is a fixed position on a chromosome such as the position of a genetic marker that may be occupied by one or more genes....
.

t(2;5)(p23;q35) - anaplastic large cell lymphoma
Anaplastic large cell lymphoma

Anaplastic large cell lymphoma is a type of non-Hodgkin lymphoma that features in the World Health Organisation classification of lymphomas....
t(8;14) - Burkitt's lymphoma
Burkitt's lymphoma

Burkitt lymphoma is a cancer of the lymphatic system . It is named after Denis Parsons Burkitt, a surgeon who first described the disease in 1956 while working in equatorial Africa....
(c-myc)
t(9;22)(q34;q11) - Philadelphia chromosome
Philadelphia chromosome

Philadelphia chromosome or Philadelphia translocation is a specific chromosome abnormality that is associated with chronic myelogenous leukemia ....
, CML
Chronic myelogenous leukemia

Chronic myelogenous leukemia , also known as chronic granulocytic leukemia , is a form of leukemia characterized by the increased and unregulated growth of predominantly myeloid cells in the bone marrow and the accumulation of these cells in the blood....
, 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....
t(11;14) - Mantle cell lymphoma
Mantle cell lymphoma

Mantle cell lymphoma is one of the rarer of the Non-Hodgkin lymphoma , comprising about 6% of NHL cases. There are only about 15,000 patients presently in the U.S....
(Bcl-1)
t(11;22)(q24;q11.2-12) - Ewing's sarcoma
Ewing's sarcoma

Ewing sarcoma is a malignant round-cell tumor. It is a rare disease in which cancer cells are found in the bone or in soft biological tissue. The most common areas in which it occurs are the pelvis, the femur, the humerus, and the ribs....
t(14;18)(q32;q21) - follicular lymphoma
Follicular lymphoma

Follicular lymphoma is the most common of the indolent non-Hodgkin's lymphomas. It is defined as a lymphoma of lymph follicle center B-cells , which has at least a partially follicular pattern....
(Bcl-2
Bcl-2

Bcl-2 is the prototype for a family of mammalian genes and the proteins they produce. They govern mitochondrial outer membrane permeabilization and can be either pro-apoptosis or anti-apoptotic ....
)
t(17;22) - dermatofibrosarcoma protuberans
Dermatofibrosarcoma protuberans

Dermatofibrosarcoma protuberans is a rare neoplasm of the dermis layer of the skin, and is classified as a sarcoma. In many respects, the disease behaves as a benign tumor, but in 2-5% of cases it can metastasis, so it should be considered to have malignant potential....
t(15;17) - acute promyelocytic leukemia
Acute promyelocytic leukemia

Acute promyelocytic leukemia is a subtype of acute myelogenous leukemia , a cancer of the blood and bone marrow. It is also known as acute progranulocytic leukemia; APL; AML with t, PML-RARA and variants; FAB subtype M3 and M3 variant....
t(1;12)(q21;p13) - acute myelogenous leukemia
t(9;12)(p24;p13) - CML
Chronic myelogenous leukemia

Chronic myelogenous leukemia , also known as chronic granulocytic leukemia , is a form of leukemia characterized by the increased and unregulated growth of predominantly myeloid cells in the bone marrow and the accumulation of these cells in the blood....
, 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....
(TEL-JAK2
TEL-JAK2

TEL-JAK2 is a fusion gene resulting from a chromosomal translocation between chromosomes chromosome 9 and chromosome 12 observed in human leukemia ....
)
t(X;18)(p11.2;q11.2) - Synovial sarcoma
Sarcoma

A sarcoma is a cancer of the connective tissue resulting in mesoderm proliferation.This is in contrast to Carcinoma, which are of Epithelium origin ....
t(1;11)(q42.1;q14.3)- Schizophrenia
Schizophrenia

Schizophrenia , from the Ancient Greek Root schizein and phren, phren- is a psychiatry diagnosis that describes a mental disorder characterized by abnormalities in the perception or expression of reality....
t(12;15)(p13;q25) - (TEL-TrkC); acute myeloid leukemia, congenital fibrosarcoma, secretory breast carcinoma

Named translocations

Philadelphia chromosome
Philadelphia chromosome

Philadelphia chromosome or Philadelphia translocation is a specific chromosome abnormality that is associated with chronic myelogenous leukemia ....
Robertsonian translocation
Robertsonian translocation

Robertsonian translocation is a common form of chromosomal rearrangement that occurs in the five Centromere#Acrocentric human chromosome pairs, namely 13, 14, 15, 21, and 22....