Humans normally have 46 chromosomes in each cell, divided into 23
pairs. Two copies of chromosome 8, one copy inherited from each parent,
form one of the pairs. Chromosome 8 spans more than 146 million DNA
building blocks (base pairs) and represents between 4.5 and 5 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 8 likely contains about 700 genes that provide instructions for making proteins. These proteins perform a variety of different roles in the body.
Genes on chromosome 8 are among the estimated 20,000 to 25,000 total genes in the human genome.
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 8 likely contains about 700 genes that provide instructions for making proteins. These proteins perform a variety of different roles in the body.
Genes on chromosome 8 are among the estimated 20,000 to 25,000 total genes in the human genome.
How are changes in chromosome 8 related to health conditions?
Many genetic conditions are related to changes in particular genes on chromosome 8.
This list of disorders associated with genes on chromosome 8 provides links to additional information.
Changes in the structure or number of copies of a chromosome can also cause problems with health and development. The following chromosomal conditions are associated with such changes in chromosome 8.
Changes in the structure or number of copies of a chromosome can also cause problems with health and development. The following chromosomal conditions are associated with such changes in chromosome 8.
- Langer-Giedion syndrome
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Langer-Giedion syndrome is caused by a deletion or mutation in
several genes on the long (q) arm of chromosome 8 at a position
described as 8q24.1. This condition causes bone abnormalities, including
noncancerous bone tumors known as exostoses, and distinctive facial
features. The signs and symptoms of this condition are related to the
deletion or mutation in at least two genes from this part of the
chromosome. Researchers have determined that the loss of a functional EXT1
gene is responsible for the multiple noncancerous (benign) bone tumors
called exostoses seen in people with Langer-Giedion syndrome. Loss of a
functional TRPS1 gene may cause the other bone and facial abnormalities. One copy of the EXT1 gene and the TRPS1
gene are always missing or mutated in affected individuals; however,
neighboring genes may also be involved. The loss of additional genes
from this region of chromosome 8 likely contributes to the varied
features of Langer-Giedion syndrome.
- 8p11 myeloproliferative syndrome
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Translocations of genetic material between chromosome 8 and other
chromosomes can cause 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. The most common translocation
involved in this condition, written as t(8;13)(p11;q12), fuses part of
the FGFR1 gene on chromosome 8 with part of the ZMYM2 gene on chromosome 13. The translocations are found 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 gene, regardless of the partner gene involved, leads to constant FGFR1 signaling. The uncontrolled signaling promotes continuous cell growth and division, leading to cancer.
- recombinant 8 syndrome
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A rearrangement of chromosome 8 causes recombinant 8 syndrome, a
condition that involves heart and urinary tract abnormalities, moderate
to severe intellectual disability, and a distinctive facial appearance.
This rearrangement results in a deletion of a piece of the short (p) arm
and a duplication of a piece of the long (q) arm. This chromosome
abnormality is written rec(8)dup(8q)inv(8)(p23.1q22.1). The signs and
symptoms of recombinant 8 syndrome are related to the loss of genetic
material on the short arm of chromosome 8 and the presence of extra
genetic material on the long arm of chromosome 8. Researchers are
working to determine which genes are involved in the deletion and
duplication on chromosome 8.
- other cancers
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Translocations between chromosome 8 and other chromosomes have been
associated with other types of cancer. For example, Burkitt lymphoma (a
cancer of white blood cells called B cells that occurs most often in
children and young adults) can be caused by a translocation between
chromosomes 8 and 14. This translocation, written t(8;14)(q24;q32),
leads to continuous cell division without control or order, which likely
contributes to the development of Burkitt lymphoma. Less frequently,
Burkitt lymphoma can be caused by translocations between chromosomes 8
and 2 or chromosomes 8 and 22.
- other chromosomal conditions
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Trisomy 8 occurs when cells have three copies of chromosome 8 instead
of the usual two copies. Full trisomy 8, which occurs when all of the
body's cells contain an extra copy of chromosome 8, is not compatible
with life. A similar but less severe condition called mosaic trisomy 8
occurs when only some of the body's cells have an extra copy of
chromosome 8. The signs and symptoms of mosaic trisomy 8 vary widely and
can include intellectual disability, absence of the tissue connecting
the left and right halves of the brain (corpus callosum), skeletal
defects, heart problems, kidney and liver malformations, and facial
abnormalities. Trisomy 8 mosaicism is also associated with an increased
risk of a specific type of cancer of blood-forming cells called acute
myelogenous leukemia.
Another chromosomal condition called inversion duplication 8p is caused by a rearrangement of genetic material on the short (p) arm of chromosome 8. This rearrangement results in an abnormal duplication and an inversion of a segment of the chromosome. An inversion involves the breakage of a chromosome in two places; the resulting piece of DNA is reversed and reinserted into the chromosome. People with inversion duplication 8p typically have severe intellectual disability, a thin or absent corpus callosum, weak muscle tone (hypotonia), abnormal curvature of the spine (scoliosis), and minor facial abnormalities. Some individuals with this condition may also have heart defects, underdeveloped kidneys, or eye abnormalities. Older individuals usually develop abnormal muscle stiffness (spasticity). The signs and symptoms of inversion duplication 8p tend to depend on the size and location of the chromosome segment involved. For example, inclusion of chromosome region 8p21 is thought to be associated with more severe symptoms.
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