Thursday, March 6, 2014
Living with CTM
This video shows many people who live with CMT and their individual struggles with the disease.
Effect of Genotype on Phenotype
Charcot-Marie-Tooth disorder, CMT, has considerable effects on someone with this genetic disorder caused by one small duplication on chromosome 17.
CMT at it's very roots is a gene that calls to make to much of a protein that lines the cell axons. These axons allow electric signals to be sent from the muscles to the brain. The protein that lines them, myelin, protects these axons. When there is to much, or a build up of myelin, as caused by CMT, signals cannot get through.
Patients with CMT most commonly have muscle weakness in the lower half of their body. Extremely high arches in the feet, a foot drop, and "inverted champagne bottle legs" are all symptoms cause by excessive muscle weakness, due to CMT. CMT patients also report lots of tripping. In more severe cases, atrophy in the hands occurs and in the most severe cases, a patient requires leg braces.
CMT at it's very roots is a gene that calls to make to much of a protein that lines the cell axons. These axons allow electric signals to be sent from the muscles to the brain. The protein that lines them, myelin, protects these axons. When there is to much, or a build up of myelin, as caused by CMT, signals cannot get through.
Patients with CMT most commonly have muscle weakness in the lower half of their body. Extremely high arches in the feet, a foot drop, and "inverted champagne bottle legs" are all symptoms cause by excessive muscle weakness, due to CMT. CMT patients also report lots of tripping. In more severe cases, atrophy in the hands occurs and in the most severe cases, a patient requires leg braces.
Works Cited
http://www.biotechnologyonline.gov.au/popups/img_karyotype.html
https://www.bcm.edu/news/molecular-and-human-genetics/charcot-marie-tooth-gene-triplication
http://www.ninds.nih.gov/disorders/charcot_marie_tooth/detail_charcot_marie_tooth.htm
http://mda.org/disease/charcot-marie-tooth/signs-and-symptoms
http://www.footeducation.com/charcot-marie-tooth-disease-cmt-foot-deformities
http://wfffun.info/diseases/charcot-marie-tooth-legs-6/
https://www.bcm.edu/news/molecular-and-human-genetics/charcot-marie-tooth-gene-triplication
http://www.ninds.nih.gov/disorders/charcot_marie_tooth/detail_charcot_marie_tooth.htm
http://mda.org/disease/charcot-marie-tooth/signs-and-symptoms
http://www.footeducation.com/charcot-marie-tooth-disease-cmt-foot-deformities
http://wfffun.info/diseases/charcot-marie-tooth-legs-6/
When and Where?
Charcot-Marie-Tooth disorder, or CMT for short, is inherited by one's parents. This was discovered in the 1930's by geneticist Calvin Bridges. In 1991, bad news turned to worse news when Dr. James Lupski, professor at the Baylor College of Medicine, discovered that as the disease is passed down through generations, it becomes more severe.
CMT occurs when a band on chromosome 17 is duplicated. During S phase in Interphase, DNA is replicated and this is when the duplication occurs. However, this disorder is not so simple. As Dr. Lupski discovered in 1991, if someone with this duplication reproduces, their child will have a triplication of the band and therefore inherit a more severe case of the disease.
Dr. Lupski and his colleague, Dr. Lui, believe that a triplication would continue onto the next offspring, as the duplication did, but it has not been tested because of how severe the effects of the triplicated CMT is.
There a several variations of the CMT disease, but all forms (tested by doctors that did not know who had what version of CMT) held the pattern that duplications increased to triplications in the next generation.
CMT occurs when a band on chromosome 17 is duplicated. During S phase in Interphase, DNA is replicated and this is when the duplication occurs. However, this disorder is not so simple. As Dr. Lupski discovered in 1991, if someone with this duplication reproduces, their child will have a triplication of the band and therefore inherit a more severe case of the disease.
Dr. Lupski and his colleague, Dr. Lui, believe that a triplication would continue onto the next offspring, as the duplication did, but it has not been tested because of how severe the effects of the triplicated CMT is.
There a several variations of the CMT disease, but all forms (tested by doctors that did not know who had what version of CMT) held the pattern that duplications increased to triplications in the next generation.
Karyotype
Because the Charcot-Marie-Tooth disorder is inherited, it is very difficult to see where the mistake is. Some genetic disorders, like Downs syndrome, have a very obvious mistake (Downs syndrome, an extra 21st chromosome), but as you can see, the karyotype does not show any obvious differences to someone without a genetic disorder.
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