Chromosome 15


Chromosome 15 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 15 spans about 101 million base pairs and represents between 3% and 3.5% of the total DNA in cells.
The human leukocyte antigen gene for β2-microglobulin is found at chromosome 15.

Genes

Number of genes

The following are some of the gene count estimates of human chromosome 15. Because researchers use different approaches to genome annotation their predictions of the number of genes on each chromosome varies. Among various projects, the collaborative consensus coding sequence project takes an extremely conservative strategy. So CCDS's gene number prediction represents a lower bound on the total number of human protein-coding genes.
Estimated byProtein-coding genesNon-coding RNA genesPseudogenesSourceRelease date
CCDS561——2016-09-08
HGNC5593284332017-05-12
Ensembl6059925082017-03-29
UniProt601——2018-02-28
NCBI6297165942017-05-19

Gene list

The following is a partial list of genes on human chromosome 15. For complete list, see the link in the infobox on the right.

Chromosomal conditions

The following conditions are caused by mutations in chromosome 15. Two of the conditions involve a loss of gene activity in the same part of chromosome 15, the 15q11.2-q13.1 region. This discovery provided the first evidence in humans that something beyond genes could determine how the genes are expressed.

Angelman syndrome

The main characteristics of Angelman syndrome are severe intellectual disability, ataxia, lack of speech, and excessively happy demeanor. Angelman syndrome results from a loss of gene activity in a specific part of chromosome 15, the 15q11-q13 region. This region contains a gene called UBE3A that, when mutated or absent, likely causes the characteristic features of this condition. People normally have two copies of the UBE3A gene, one from each parent. Both copies of this gene are active in many of the body's tissues. In the brain, however, only the copy inherited from a person's mother is active. If the maternal copy is lost because of a chromosomal change or a gene mutation, a person will have no working copies of the UBE3A gene in the brain.
In most cases, people with Angelman syndrome have a deletion in the maternal copy of chromosome 15. This chromosomal change deletes the region of chromosome 15 that includes the UBE3A gene. Because the copy of the UBE3A gene inherited from a person's father is normally inactive in the brain, a deletion in the maternal chromosome 15 results in no active copies of the UBE3A gene in the brain.
In 3% to 7% of cases, Angelman syndrome occurs when a person has two copies of the paternal chromosome 15 instead of one copy from each parent. This phenomenon is called paternal uniparental disomy. People with paternal UPD for chromosome 15 have two copies of the UBE3A gene, but they are both inherited from the father and are therefore inactive in the brain.
About 10% of Angelman syndrome cases are caused by a mutation in the UBE3A gene, and another 3% result from a defect in the DNA region that controls the activation of the UBE3A gene and other genes on the maternal copy of chromosome 15. In a small percentage of cases, Angelman syndrome may be caused by a chromosomal rearrangement called a translocation or by a mutation in a gene other than UBE3A. These genetic changes can abnormally inactivate the UBE3A gene.
Angelman syndrome can be hereditary, as evidenced by one case where a patient became pregnant with a daughter who also had the condition.

Prader–Willi syndrome

The main characteristics of this condition include polyphagia, mild to moderate developmental delay, hypogonadism resulting in delayed to no puberty, and hypotonia. Prader-Willi syndrome is caused by the loss of active genes in a specific part of chromosome 15, the 15q11-q13 region. People normally have two copies of this chromosome in each cell, one copy from each parent. Prader–Willi syndrome occurs when the paternal copy is partly or entirely missing.
In about 70% of cases, Prader–Willi syndrome occurs when the 15q11-q13 region of the paternal chromosome 15 is deleted. The genes in this region are normally active on the paternal copy of the chromosome and are inactive on the maternal copy. Therefore, a person with a deletion in the paternal chromosome 15 will have no active genes in this region.
In about 25% of cases, a person with Prader–Willi syndrome has two maternal copies of chromosome 15 in each cell instead of one copy from each parent. This phenomenon is called maternal uniparental disomy. Because some genes are normally active only on the paternal copy of this chromosome, a person with two maternal copies of chromosome 15 will have no active copies of these genes.
In a small percentage of cases, Prader–Willi syndrome is not caused by a chromosomal rearrangement called a trans location. Rarely, the condition is caused by an abnormality in the DNA region that controls the activity of genes on the paternal chromosome 15. Because patients almost always have difficulty reproducing, Prader–Willi syndrome is generally not hereditary.

Isodicentric chromosome 15

A specific chromosomal change called an isodicentric chromosome 15 can affect growth and development. The patient possesses an "extra" or "marker" chromosome. This small extra chromosome is made up of genetic material from chromosome 15 that has been abnormally duplicated and attached end-to-end. In some cases, the extra chromosome is very small and has no effect on a person's health. A larger isodicentric chromosome 15 can result in weak muscle tone, mental retardation, seizures, and behavioral problems. Signs and symptoms of autism have also been associated with the presence of an isodicentric chromosome 15.

Other chromosomal conditions

Other changes in the number or structure of chromosome 15 can cause mental retardation, delayed growth and development, hypotonia, and characteristic facial features. These changes include an extra copy of part of chromosome 15 in each cell or a missing segment of the chromosome in each cell. In some cases, several of the chromosome's DNA building blocks are deleted or duplicated.
The following diseases are some of those related to genes on chromosome 15:
Chr.ArmBandISCN
start		ISCN
stop		Basepair
start		Basepair
stop		StainDensity
15p130270gvar
15p12270631stalk
15p11.26311142gvar
15p11.111421382acen
15q11.113821487acen
15q11.214871773gneg
15q1217731968gpos50
15q13.119682164gneg
15q13.221642284gpos50
15q13.322842524gneg
15q1425242765gpos75
15q15.127652975gneg
15q15.229753065gpos25
15q15.330653245gneg
15q21.132453471gpos75
15q21.234713621gneg
15q21.336213846gpos75
15q22.138463982gneg
15q22.239824087gpos25
15q22.3140874252gneg
15q22.3242524357gpos25
15q22.3343574507gneg
15q2345074613gpos25
15q24.146134748gneg
15q24.247484808gpos25
15q24.348084928gneg
15q25.149285048gpos50
15q25.250485169gneg
15q25.351695379gpos50
15q26.153795649gneg
15q26.256495860gpos50
15q26.358606070gneg