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Chromosome 8
Home of the MYC oncogene at 8q24 - one of the most-studied cancer drivers in biology.
Schematic of chromosome 8 showing the short (p) and long (q) arms. Arm ratio per GRCh38 - banding schematic.
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Overview
Chromosome 8 is the eighth-largest human chromosome by physical size, measuring approximately 145.1 megabases (Mb) in length. It represents about 4.5 per cent of the total DNA in each cell and carries an estimated 685 protein-coding genes. The chromosome is classified as submetacentric, meaning the centromere - the pinched region that anchors spindle fibres during cell division - sits somewhat off-centre, creating a short arm (8p) and a distinctly longer arm (8q).
Chromosome 8 is widely recognised in clinical and research circles for hosting the MYC gene at 8q24, a master regulator of cell growth and proliferation that is implicated in a wide range of human cancers. When MYC expression becomes inappropriately elevated through amplification or translocation events, cells may begin dividing without normal restraints, a hallmark of malignant transformation. Beyond MYC, chromosome 8 also carries genes involved in DNA-damage response, skeletal development, and neurological function, underscoring its importance across multiple physiological systems.
Unlike some other chromosomes, chromosome 8 is not commonly associated with whole-chromosome aneuploidies (such as trisomy or monosomy) that are compatible with survival to birth. Trisomy 8 is occasionally seen in mosaic form - where only some cells carry an extra copy - but complete trisomy 8 is typically lethal in early pregnancy. Instead, the clinical relevance of chromosome 8 tends to centre on structural rearrangements (translocations, deletions, amplifications) and point mutations within specific genes, particularly in the context of cancer and rare developmental disorders.
Structure
Like all human chromosomes, chromosome 8 has two distinct arms separated by the centromere. The short arm, designated 8p, extends from the tip (the telomere at 8pter) down to the centromere, whilst the long arm, 8q, runs from the centromere to the opposite telomere at 8qter. Because the centromere sits off-centre, the q arm is noticeably longer than the p arm, giving the chromosome its submetacentric classification. During metaphase - the stage of cell division when chromosomes are most condensed and visible under a microscope - chromosome 8 appears as an X-shaped structure with asymmetric branches.
At the molecular level, the roughly 145 million DNA base pairs of chromosome 8 are packaged through multiple layers of organisation. The double-helix DNA strand wraps around histone proteins to form nucleosomes, which in turn coil into chromatin fibres. During cell division, this chromatin condenses further into the compact chromosome structure visible on a karyotype. Different regions of the chromosome adopt varying degrees of compaction even in non-dividing cells: gene-rich, transcriptionally active areas tend to remain relatively open (euchromatin), whilst gene-poor or silenced regions are more tightly packed (heterochromatin). This dynamic packaging helps regulate which genes are accessible for transcription at any given time, contributing to cell-type-specific gene expression.
Video: What is a karyotype?
Notable regions
One of the most intensively studied regions of chromosome 8 is 8q24.21, home to the MYC gene. MYC encodes a transcription factor that controls the expression of hundreds of other genes involved in cell growth, metabolism, and division. Evidence suggests that when MYC is overexpressed - whether through gene amplification, chromosomal translocation, or other regulatory disruptions - it can drive the uncontrolled proliferation characteristic of many cancers, including Burkitt lymphoma, certain breast and colorectal cancers, and some leukaemias. In Burkitt lymphoma, for example, a translocation between chromosome 8 and chromosome 14 places MYC next to an immunoglobulin gene promoter, leading to sustained high-level MYC expression in B cells. The 8q24 region additionally contains several long-range regulatory elements that influence cancer risk in genome-wide association studies.
Further along the short arm, at 8p11.23, lies FGFR1, which encodes fibroblast growth factor receptor 1. This receptor tyrosine kinase plays a crucial role in early development, influencing cell migration, differentiation, and tissue patterning. Pathogenic variants in FGFR1 are associated with a spectrum of developmental conditions, including Kallmann syndrome (characterised by delayed or absent puberty and impaired sense of smell) and certain forms of craniosynostosis, where skull bones fuse prematurely. Structural rearrangements involving FGFR1 have also been identified in some haematological malignancies, underscoring the gene's dual relevance to both development and cancer.
The 8q22.3 region contains VPS13B, a large gene in which pathogenic variants cause Cohen syndrome, a rare autosomal-recessive condition. Individuals with Cohen syndrome typically present with developmental delay, intellectual disability, characteristic facial features, and progressive vision loss due to retinal degeneration. The VPS13B protein is thought to be involved in intracellular trafficking and membrane dynamics, though the precise molecular mechanisms linking VPS13B dysfunction to the wide-ranging features of Cohen syndrome remain an active area of research.
Notable genes
Beyond MYC, FGFR1, and VPS13B, chromosome 8 hosts several other genes of broad clinical and research interest. The WRN gene at 8p12 encodes a DNA helicase critical for maintaining genomic stability, particularly during DNA replication and repair. Biallelic pathogenic variants in WRN cause Werner syndrome, a rare disorder characterised by premature ageing, early-onset cataracts, skin changes, and an elevated risk of cancer. The NBN gene at 8q21.3 encodes nibrin, a component of the DNA double-strand-break repair machinery. Loss-of-function variants in NBN lead to Nijmegen breakage syndrome, marked by microcephaly, immunodeficiency, growth retardation, and a greatly increased risk of lymphoid malignancies. Both WRN and NBN highlight the importance of chromosome 8 in DNA-damage response pathways, with disruptions in these genes predisposing to both developmental abnormalities and cancer.
Chromosomal disorders
Complete trisomy 8 - the presence of three copies of chromosome 8 in every cell - is generally incompatible with survival beyond early pregnancy. However, mosaic trisomy 8, where only a proportion of cells carry the extra chromosome, can occur and presents with a highly variable clinical picture. Features may include growth restriction, intellectual disability, skeletal abnormalities, kidney malformations, and characteristic facial appearance, though the severity depends on the percentage of trisomic cells and which tissues are affected. Mosaic trisomy 8 is typically detected postnatally, either through karyotyping prompted by developmental concerns or incidentally during evaluation for another indication. It is not routinely screened for in standard prenatal screening panels, which focus on the common autosomal trisomies (chromosomes 13, 18, and 21).
Structural abnormalities of chromosome 8 are more commonly encountered in clinical practice than whole-chromosome aneuploidies. Microdeletions and microduplications - small missing or extra segments of the chromosome - can arise de novo or be inherited from a parent carrying a balanced rearrangement. For example, deletions in the 8p23.1 region have been associated with developmental delay, congenital heart defects, and behavioural difficulties, whilst duplications involving 8q can lead to overgrowth, intellectual disability, and dysmorphic features. The specific clinical consequences depend on which genes are encompassed by the deleted or duplicated segment. Chromosomal microarray analysis, a high-resolution technique that detects copy-number changes across the genome, is often used within NHS genetics services to identify such imbalances when a child presents with unexplained developmental delay or multiple congenital anomalies.
Translocations involving chromosome 8 are particularly relevant in haematological malignancies. The classic example is the translocation between chromosomes 8 and 14, t(8;14), seen in Burkitt lymphoma, which repositions MYC under the control of immunoglobulin regulatory elements. Other translocations, such as those involving FGFR1 at 8p11, have been documented in certain myeloproliferative disorders. These acquired chromosomal rearrangements occur in tumour cells and are not inherited in the germline, but their detection through karyotyping or fluorescence in situ hybridisation (FISH) can inform diagnosis, prognosis, and treatment decisions in oncology.
Prenatal screening & diagnosis
Abnormalities of chromosome 8 are not included in the standard aneuploidy panel offered through routine NHS prenatal screening. The combined first-trimester screening (which assesses risk for trisomies 21, 18, and 13 using maternal serum markers and ultrasound nuchal-translucency measurement) and non-invasive prenatal testing (NIPT) both focus on the more common autosomal trisomies and, in some cases, sex-chromosome aneuploidies. Mosaic trisomy 8 and structural abnormalities of chromosome 8 are therefore typically discovered postnatally, often during investigation of developmental concerns, dysmorphic features, or congenital anomalies.
When a structural rearrangement involving chromosome 8 is suspected - perhaps because of ultrasound findings such as congenital heart defects or growth restriction - a diagnostic test may be offered. This usually involves chorionic villus sampling (CVS) in the first trimester or amniocentesis in the second trimester, followed by karyotyping or chromosomal microarray to identify deletions, duplications, or translocations. If a parent is known to carry a balanced translocation involving chromosome 8, prenatal diagnosis may be offered in future pregnancies to determine whether the fetus has inherited the balanced form, an unbalanced form, or normal chromosomes. Genetic counselling through NHS clinical genetics services helps families understand the implications of any findings and the options available.
Inheritance & recurrence
Most structural abnormalities of chromosome 8 identified in children arise de novo, meaning they occur as new events during the formation of the egg or sperm, or in early embryonic development, and are not present in either parent. In such cases, the recurrence risk for future siblings is generally low, only slightly above the background population risk. However, if parental chromosomal analysis reveals that one parent carries a balanced rearrangement (such as a balanced translocation or inversion involving chromosome 8), the recurrence risk can be substantially higher, because the parent may produce gametes with unbalanced chromosome complements. The exact risk depends on the nature and breakpoints of the rearrangement.
For autosomal-recessive conditions caused by pathogenic variants in genes on chromosome 8 - such as Cohen syndrome (VPS13B), Werner syndrome (WRN), or Nijmegen breakage syndrome (NBN) - each pregnancy between two carrier parents carries the standard Mendelian inheritance pattern: affected, carrier, and unaffected outcomes are all possible. Families with a known history of such conditions are typically offered cascade carrier testing for at-risk relatives and prenatal or preimplantation genetic diagnosis options. Referral to a regional NHS genomic medicine service centre ensures access to specialist genetic counselling and testing tailored to the family's specific situation.
Frequently asked questions
What is chromosome 8 best known for?
Chromosome 8 is best known for carrying the MYC gene at 8q24, one of the most-studied oncogenes in cancer research. MYC dysregulation is implicated in many human cancers, including Burkitt lymphoma, breast cancer, and colorectal cancer. The chromosome also hosts genes involved in DNA repair and development, such as WRN and FGFR1.
Can you have an extra copy of chromosome 8?
Complete trisomy 8 (three copies in all cells) is usually not compatible with survival beyond early pregnancy. However, mosaic trisomy 8, where only some cells have an extra copy, can occur and leads to variable features including developmental delay, growth restriction, and organ anomalies. Mosaic trisomy 8 is typically diagnosed postnatally, not through routine prenatal screening.
Are abnormalities of chromosome 8 screened for during pregnancy?
Routine NHS prenatal screening (combined first-trimester screening and non-invasive prenatal testing) focuses on the common trisomies: chromosomes 21, 18, and 13. Abnormalities of chromosome 8 are not included in standard screening panels and are usually detected only if diagnostic testing (amniocentesis or chorionic villus sampling) is performed for another indication, such as abnormal ultrasound findings.
What is the 8q24 region and why does it matter in cancer?
The 8q24 region contains the MYC gene and several long-range regulatory elements. MYC is a transcription factor controlling cell growth and division; when overexpressed due to gene amplification or chromosomal translocation, it can drive uncontrolled cell proliferation. The t(8;14) translocation in Burkitt lymphoma, for instance, places MYC under the control of an immunoglobulin promoter, leading to sustained MYC expression and lymphoma development.
If my child has a deletion or duplication on chromosome 8, what does that mean?
A deletion or duplication means a small segment of chromosome 8 is missing or present in extra copies. The clinical impact depends on which genes are affected. Some deletions or duplications cause developmental delay, congenital anomalies, or intellectual disability, whilst others may have minimal effect. Your NHS clinical genetics team will interpret the specific finding, check parental chromosomes, and provide tailored counselling about recurrence risk and management.
Launch-set genes on chromosome 8
Genes on this chromosome that currently have dedicated pages in the library. This list grows as we publish more.