Chromosome 18

Chromosome 18 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 18 spans about 80 million base pairs (the building material of DNA) and represents about 2.5 percent of the total DNA in cells.

Structure

The chromosome has two arms, the short arm 'p' and the long arm 'q'. The centromere, which is the point of constriction, separates the two arms. This point is the attachment point for spindle fibers during cell division.

Genes

Chromosome 18 contains about 300 to 400 genes. Some of these genes include:

• DCC: This gene is involved in guiding the growth of axons in the nervous system.
• SMAD4: This gene is involved in the transmission of chemical signals from the cell surface to the nucleus.
• TCF4: This gene is involved in the development of the nervous system.

Diseases and disorders

Several diseases and disorders are related to genes on chromosome 18. These include:

• Tetrasomy 18p: This is a rare genetic disorder caused by the presence of four copies (instead of the usual two) of the short arm of chromosome 18.
• Chromosome 18q deletion syndrome: This is a syndrome caused by a deletion of genetic material from the long arm of chromosome 18.
• Edwards syndrome: This is a condition caused by an extra copy of chromosome 18.

Research

Research is being conducted to find links between the genes on chromosome 18 and diseases such as colorectal cancer, head and neck cancer, and pancreatic cancer.

See also

• List of conditions caused by problems with chromosomes

External links

• National Center for Biotechnology Information (NCBI): Chromosome 18

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Chromosome_18

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  Chromosome 18 cropped from a high-resolution human male karyotype

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  Chromosome 18 from a high-resolution human male karyotype

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  Ideogram of human chromosome 18

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  Human chromosome 18 at different banding resolutions (400, 550, 850 bphs)