MadSci Network: Genetics |
Although the complete loss of chromosome 18 results in abortion very early in pregnancy, the results of a smaller deletion will depend on its location and size. Several tumor-suppressor genes occur on this chromosome, so some deletions would likely render patients more prone to cancer. In several types of tumor, and in particular colon cancer, deletions of chromosome 18 are very common. So we have one effect there. [1] If the short arm of chromosome 18 is lost, de Grouchy syndrome 1 (or 18p- syndrome) results. This is actually a pretty common deletion, and results in mental retardation (associated with a failure of the brain to furrow normally in the developing fetus), cleft palate, and other varying results. [2] If, on the other hand, we lose the long arm of chromosome 18, we get de Grouchy syndrome 2 (18q- syndrome), which also leads to mental retardation. The symptoms vary, though, and may include growth retardation. [3] I hope that this is helpful; the links below give much, much more thorough descriptions of the deletion syndromes. Paul Nagami References: 1. Jackson, KE et al. (2000) Phenotypic features in a boy with monosomy 18 mosaicism. American Journal of Medical Genetics 95(3):229-232 2. "chromosome 18p deletion syndrome." (1999) Jablonski's Multiple Congenital Anomaly/Mental Retardation (MCA/MR) Syndromes Database, at the US National Library of Medicine website: http://www.nlm.nih.gov/mesh/jablonski/syndromes/syndrome192.html 3. "chromosome 18q deletion syndrome." (1999) Jablonski's Multiple Congenital Anomaly/Mental Retardation (MCA/MR) Syndromes Database, at the US National Library of Medicine website: http://www.nlm.nih.gov/cgi/jablonski/syndrome_cgi?index=194
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