Chromosome 5

The following conditions are caused by changes in the structure or number of copies of chromosome 5.

cancers

Changes in the structure of chromosome 5 are associated with certain forms of cancer and conditions related to cancer. These changes are typically somatic, which means they are acquired during a person's lifetime and are present only in tumor cells. Deletions in the long (q) arm of the chromosome have been identified in a form of blood cancer known as acute myeloid leukemia (AML). These deletions also frequently occur in a disorder called myelodysplastic syndrome, which is a disease of the blood and bone marrow. People with this condition have a low number of red blood cells (anemia) and an increased risk of developing AML. When myelodysplastic syndrome is associated with a specific deletion in the long arm of chromosome 5, it is known as 5q- (5q minus) syndrome. Studies are under way to determine which genes in the deleted region of chromosome 5 are related to myelodysplastic syndrome and AML.

cri-du-chat syndrome

Cri-du-chat syndrome is caused by a deletion of the end of the short (p) arm of chromosome 5. This chromosomal change is written as 5p- (5p minus). The signs and symptoms of cri-du-chat syndrome are probably related to the loss of multiple genes in this region. Researchers are working to identify all of these genes and determine how their loss leads to the features of the disorder. They have discovered that in people with cri-du-chat syndrome, larger deletions tend to result in more severe intellectual disability and developmental delays than smaller deletions. They have also defined regions of the short arm of chromosome 5 that are associated with particular features of cri-du-chat syndrome. A specific region designated 5p15.3 is associated with a cat-like cry, and a nearby region called 5p15.2 is associated with intellectual disability, small head size (microcephaly), and distinctive facial features.

Crohn disease

Several regions of chromosome 5 have been associated with the risk of developing Crohn disease. For example, a combination of genetic variations in a region of DNA on the long (q) arm of the chromosome (5q31) has been shown to increase a person's chance of developing Crohn disease. Taken together, these variations are known as the inflammatory bowel disease 5 (IBD5) locus. This region of chromosome 5 contains several related genes that may be associated with Crohn disease risk, including SLC22A4 and SLC22A5.

Variations in a region of the short (p) arm of chromosome 5 designated 5p13.1 are also associated with Crohn disease risk. Researchers refer to this part of chromosome 5 as a "gene desert" because it contains no known genes; however, it may contain stretches of DNA that help regulate nearby genes such as PTGER4. Research studies are under way to examine a possible connection between the PTGER4 gene and Crohn disease.

periventricular heterotopia

In a few cases, abnormalities in chromosome 5 have been associated with periventricular heterotopia, a disorder characterized by abnormal clumps of nerve cells (neurons) around fluid-filled cavities (ventricles) near the center of the brain. In each case, the affected individual had extra genetic material caused by an abnormal duplication of part of this chromosome. It is not known how this duplicated genetic material results in the signs and symptoms of periventricular heterotopia.

other chromosomal conditions

Other changes in the number or structure of chromosome 5 can have a variety of effects, including delayed growth and development, distinctive facial features, birth defects, and other medical problems. Changes to chromosome 5 include an extra segment of the short (p) or long (q) arm of the chromosome in each cell (partial trisomy 5p or 5q), a missing segment of the long arm of the chromosome in each cell (partial monosomy 5q), and a circular structure called ring chromosome 5. Ring chromosomes occur when a chromosome breaks in two places and the ends of the chromosome arms fuse together to form a circular structure.

Geneticists use diagrams called ideograms as a standard representation for chromosomes. Ideograms show a chromosome's relative size and its banding pattern. A banding pattern is the characteristic pattern of dark and light bands that appears when a chromosome is stained with a chemical solution and then viewed under a microscope. These bands are used to describe the location of genes on each chromosome.

See How do geneticists indicate the location of a gene? in the Handbook.

You may find the following resources about chromosome 5 helpful. These materials are written for the general public.

• Additional NIH Resources - National Institutes of Health
  National Human Genome Research Institute: Chromosome Abnormalities
• Educational resources - Information pages (3 links)
• MedlinePlus - Health information
  Encyclopedia: Chromosome

You may also be interested in these resources, which are designed for genetics professionals and researchers.

• Research Resources - Tools for researchers (6 links)
• PubMed - Recent literature
• OMIM - Genetic disorder catalog (4 links)
• Map Viewer - Genetic maps

The Handbook provides basic information about genetics in clear language.

• What is DNA?
• What is a chromosome?
• How many chromosomes do people have?
• Can changes in chromosomes affect health and development?

These links provide additional genetics resources that may be useful.

• Genetics education
• Human Genome Project
• Resources for Genetic Researchers

acute ; acute myelogenous leukemia ; acute myeloid leukemia ; AML ; anemia ; base pair ; bone marrow ; cancer ; cell ; chromosome ; deletion ; developmental delay ; DNA ; duplication ; gene ; genetic variation ; leukemia ; locus ; microcephaly ; monosomy ; myelodysplastic syndrome ; myelogenous ; myeloid ; nerve cell ; neuron ; red blood cell ; ring chromosomes ; sign ; symptom ; syndrome ; trisomy ; tumor ; ventricle

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.