Trisomy 18

Causes

What genetic change causes Trisomy 18?

People with trisomy 18 have an extra chromosome 18 in all of their cells. Humans generally have 46 chromosomes (23 pairs) in every cell in their body. Twenty two pairs are labelled with numbers (chromosome 1, chromosome 2, chromosome 3, etc.) and are called autosomes. The last or 23rd pair are the gender chromosomes (XX in females and XY in males). Humans generally have two copies of every chromosome, including chromosome 18. The chromosomes are comprised of genes and therefore carry our DNA. Duplicating or deleting genes can cause health problems. People with trisomy 18 have three copies of chromosome 18, and therefore have an extra set of all the genes located on this specific chromosome. Having a whole extra chromosome means there are a lot of genes with the wrong dosage (three copies instead of two copies). The extra genetic material typically leads to serious health problems.

References
  • http://ghr.nlm.nih.gov/condition/trisomy-18
  • Am J Med Genet A. 2016 Apr;170(4):825-37. doi: 10.1002/ajmg.a.37495. Epub 2015 Dec 10.Survival of children with trisomy 13 and trisomy 18: A multi-state population-based study.Meyer RE1, Liu G2, Gilboa SM3, Ethen MK4, Aylsworth AS5, Powell CM5, Flood TJ6, Mai CT3, Wang Y7, Canfield MA4; National Birth Defects Prevention Network.
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What does having an extra chromosome in Trisomy 18 cause?

What does having an extra chromosome in Trisomy 18 cause?

Chromosomes are made up of genes, and genes act as the instructions for the body. Extra or missing genetic information can lead to health problems, because there are altered instructions for the cells of the body. Adding an extra complete copy of chromosome 18 can cause heart defects, intellectual disability, defects of the brain, growth problems and other health problems.

References
  • http://ghr.nlm.nih.gov/condition/trisomy-18
  • Obstet Gynecol Surv. 2016 May;71(5):295-300. doi: 10.1097/OGX.0000000000000304.Management Considerations for Ongoing Pregnancies Complicated by Trisomy 13 and 18.Dotters-Katz SK1, Kuller JA2, Grace MR1, Laifer SA3, Strauss RA4

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