Chromosome 5

Chromosome 5 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 5 spans about 181 million base pairs (the building material of DNA) and represents almost 6 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 5 likely contains between 900 and 1,300 genes.

Genes on chromosome 5 are among the estimated 30,000 to 40,000 total genes in the human genome.

There are many conditions related to genes on chromosome 5.

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

cri-du-chat syndrome

Cri-du-chat syndrome is caused by a deletion of the end of the short (p) arm of chromosome 5 (a chromosomal change that can also be written as 5p-). The signs and symptoms of the condition are probably related to the loss of multiple genes in this region. Researchers have not yet identified all of the genes or determined why a lack of these genes leads to the characteristic features of the disorder. Researchers have discovered, however, that a larger deletion tends to result in more severe mental retardation and developmental delays in people with cri-du-chat syndrome.

Researchers have defined narrow regions of the short arm of chromosome 5 that are associated with particular features of cri-du-chat syndrome. A specific region designated 15p15.3 is associated with a cat-like cry, while a nearby region called 15p15.2 is associated with mental retardation, small head size (microcephaly), and distinctive facial features.

other chromosomal conditions

Other changes in the number or structure of chromosome 5 can have a variety of effects, including delayed growth and development, characteristic 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 that is caused by the breakage and reunion of both ends of the chromosome.

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.

• NIH Publications - National Institutes of Health
  Chromosome Abnormalities (National Human Genome Research Institute)
• Educational resources - Information pages
  Human Chromosome 5 Is Complete (Genome News Network, September 17, 2004)
• MedlinePlus - Health Information
  Encyclopedia: Chromosome

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

• Research Resources - Tools for researchers (5 links)
• PubMed - Recent literature
• 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 cause disorders?

base pair ; chromosome ; deletion ; developmental delay ; DNA ; gene ; mental retardation ; monosomy ; ring chromosomes ; sign ; symptom ; trisomy

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