Humans normally have 46 chromosomes in each cell, divided into 23 pairs. Two copies of chromosome 13, one copy inherited from each parent, form one of the pairs. Chromosome 13 is made up of about 115 million DNA building blocks (base pairs) and represents between 3.5 and 4 percent of the total DNA in cells.
Identifying genes on each chromosome is an active area of genetic research. Because researchers use different approaches to predict the number of genes on each chromosome, the estimated number of genes varies. Chromosome 13 likely contains 300 to 400 genes that provide instructions for making proteins. These proteins perform a variety of different roles in the body.
Health Conditions Related to Chromosomal Changes
The following chromosomal conditions are associated with changes in the structure or number of copies of chromosome 13.
8p11 myeloproliferative syndrome
A rearrangement (translocation) of genetic material involving chromosome 13 has been identified in most people with a rare blood cancer called 8p11 myeloproliferative syndrome. This condition is characterized by an increased number of white blood cells (myeloproliferative disorder) and the development of lymphoma, a blood-related cancer that causes tumor formation in the lymph nodes. The myeloproliferative disorder usually develops into another form of blood cancer called acute myeloid leukemia. 8p11 myeloproliferative syndrome most commonly results from a translocation between chromosome 13 and chromosome 8, written as t(8;13)(p11;q12). This genetic change fuses part of the ZMYM2 gene on chromosome 13 with part of the FGFR1 gene on chromosome 8. The translocation occurs only in cancer cells.
The protein produced from the normal FGFR1 gene can turn on cellular signaling that helps the cell respond to its environment, for example by stimulating cell growth. The protein produced from the fused ZMYM2-FGFR1 gene leads to constant FGFR1 signaling. The uncontrolled signaling promotes continuous cell growth and division, leading to cancer.More About This Health Condition
Feingold syndrome type 2 is caused by genetic changes that remove (delete) small pieces of DNA from the long (q) arm of chromosome 13. These changes are known as 13q31.3 microdeletions. Feingold syndrome type 2 is characterized by abnormalities of the fingers and toes, particularly shortening of the second and fifth fingers (brachymesophalangy). Other common features include an unusually small head size (microcephaly) and learning disabilities. 13q31.3 microdeletions involved in this condition delete the MIR17HG gene and sometimes part or all of other nearby genes. Loss of the MIR17HG gene is thought to underlie the characteristic features of the disorder, although loss of other genes may play a role in some cases.
The MIR17HG gene provides instructions for making the miR-17~92 microRNA (miRNA) cluster, which includes six different miRNAs. MiRNAs are short pieces of RNA, a chemical cousin of DNA. These molecules control gene activity (expression) by blocking protein production. MiRNAs in the miR-17~92 cluster help regulate signaling pathways that direct several cellular processes involved in growth and development before birth.
Deletion of one copy of the MIR17HG gene reduces the amount of miR-17~92 cluster miRNAs available to control the activity of specific genes during development. While it is likely that the resulting disruption of signaling pathways leads to the problems with growth and development characteristic of Feingold syndrome type 2, it is unclear exactly how a shortage of miR-17~92 cluster miRNAs causes the specific features of the condition.More About This Health Condition
Retinoblastoma, a cancer of the light-sensing tissue at the back of the eye (the retina) that affects mostly children, is caused by abnormalities of a gene called RB1. This gene is located on a region of the q arm of chromosome 13 designated 13q14. Although most retinoblastomas are caused by variants (also known as mutations) within the RB1 gene, a small percentage of retinoblastomas result from a deletion of the 13q14 region.
In addition to retinoblastoma, deletions of the 13q14 region may cause intellectual disability, slow growth, and characteristic facial features such as prominent eyebrows, a broad nasal bridge, a short nose, and ear abnormalities. A loss of several genes is likely responsible for these developmental problems, although researchers have not determined which other genes in the deleted region are involved.More About This Health Condition
Trisomy 13 occurs when each cell in the body has three copies of chromosome 13 instead of the usual two copies. Trisomy 13 can also result from an extra copy of chromosome 13 in only some of the body's cells (mosaic trisomy 13).
In some cases, trisomy 13 occurs when chromosome 13 becomes attached (translocated) to another chromosome during the formation of reproductive cells (eggs and sperm) or very early in embryonic development. Affected individuals have two copies of chromosome 13, plus extra material from chromosome 13 attached to another chromosome. People with this genetic change are said to have translocation trisomy 13. The physical signs of translocation trisomy 13 may be different from those typically seen in trisomy 13 when only part of chromosome 13 is present in three copies.
Researchers believe that extra copies of some genes on chromosome 13 disrupt the course of normal development, causing the characteristic features of trisomy 13 and the increased risk of medical problems associated with this disorder.More About This Health Condition
Other chromosomal conditions
Partial monosomy and partial trisomy of chromosome 13 occur when a portion of the q arm of this chromosome is deleted or duplicated, respectively. The effect of missing or extra chromosome material varies with the size and location of the chromosome abnormality. Affected individuals may have developmental delay, intellectual disability, low birth weight, skeletal abnormalities, and other physical features.
Changes in chromosome 13 have been associated with several types of cancer. These genetic changes are somatic, which means they are acquired during a person's lifetime and are present only in certain cells. The loss of genetic material from the middle of chromosome 13 is common in cancers of blood-forming cells (leukemias), cancers of immune system cells (lymphomas), and other related cancers.
Additional Information & Resources
Additional NIH Resources
Scientific Articles on PubMed
- Baud O, Cormier-Daire V, Lyonnet S, Desjardins L, Turleau C, Doz F. Dysmorphic phenotype and neurological impairment in 22 retinoblastoma patients with constitutional cytogenetic 13q deletion. Clin Genet. 1999 Jun;55(6):478-82. doi: 10.1034/j.1399-0004.1999.550614.x. Citation on PubMed
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- Ensembl Human Map View: Chromosome 13
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- Hemmat M, Rumple MJ, Mahon LW, Strom CM, Anguiano A, Talai M, Nguyen B, Boyar FZ. Short stature, digit anomalies and dysmorphic facial features are associated with the duplication of miR-17 ~ 92 cluster. Mol Cytogenet. 2014 Apr 16;7:27. doi: 10.1186/1755-8166-7-27. eCollection 2014. Citation on PubMed or Free article on PubMed Central
- Jackson CC, Medeiros LJ, Miranda RN. 8p11 myeloproliferative syndrome: a review. Hum Pathol. 2010 Apr;41(4):461-76. doi: 10.1016/j.humpath.2009.11.003. Citation on PubMed
- Kannu P, Campos-Xavier AB, Hull D, Martinet D, Ballhausen D, Bonafe L. Post-axial polydactyly type A2, overgrowth and autistic traits associated with a chromosome 13q31.3 microduplication encompassing miR-17-92 and GPC5. Eur J Med Genet. 2013 Aug;56(8):452-7. doi: 10.1016/j.ejmg.2013.06.001. Epub 2013 Jun 20. Erratum In: Eur J Med Genet. 2014 Feb;57(2-3):123-4. Citation on PubMed
- Kivela T, Tuppurainen K, Riikonen P, Vapalahti M. Retinoblastoma associated with chromosomal 13q14 deletion mosaicism. Ophthalmology. 2003 Oct;110(10):1983-8. doi: 10.1016/S0161-6420(03)00484-6. Citation on PubMed
- UCSC Genome Browser: Statistics
- Xiao S, Nalabolu SR, Aster JC, Ma J, Abruzzo L, Jaffe ES, Stone R, Weissman SM, Hudson TJ, Fletcher JA. FGFR1 is fused with a novel zinc-finger gene, ZNF198, in the t(8;13) leukaemia/lymphoma syndrome. Nat Genet. 1998 Jan;18(1):84-7. doi: 10.1038/ng0198-84. Citation on PubMed