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Tuesday, March 12, 2013

On the 12th Day of Trisomy Awareness...Structural Abnormalities!

DAY 12: 

On our 12th day of MARCHING into TRISOMY AWARENESS MONTH, we are going to share in more detail about STRUCTURAL ABNORMALITIES. This means that the chromosome's structure is altered, and this can come in several forms such as deletions, duplications, translocations, inversions, insertions, and rings. 

  • DELETION is when a portion of the chromosome is missing or deleted. Known disorders in humans include Wolf-Hirschhorn syndrome, which is caused by partial deletion of the short arm of chromosome 4. Jacobsen syndrome is also called the terminal 11q deletion disorder. 
  • DUPLICATION is when a portion of the chromosome is duplicated, resulting in extra genetic material. Known human disorders include Charcot-Marie-Tooth disease type 1A which may be caused by duplication of the gene encoding peripheral myelin protein 22 (PMP22) on chromosome 17. 
  • TRANSLOCATION is when a portion of one chromosome is transferred to another chromosome. There are two main types of translocations; Reciprocal translocation is when segments from two different chromosomes have been exchanged, and Robertsonian translocation is when an entire chromosome has attached to another at the centromere - in humans these only occur with chromosome 13, 14, 15, 21 and 22. 
  • INVERSION is when a portion of the chromosome has broken off, turned upside down and reattached, therefore the genetic material is inverted. 
  • INSERTION is when a portion of one chromosome has been deleted from its normal place and inserted into another chromosome. 
  • RING is when a portion of a chromosome has broken off and formed a circle or ring. This can happen with or without loss of genetic material. 

The sample picture attached shows an example of how these structural abnormalities compare to the normal. Share because you Care ♥

Visit Hope for Trisomy on Facebook for more interesting facts about chromosomes and trisomy!

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