Do you Know what is the most common cause of Mental Retardation in boys ?
Fragile -X- Syndrome ..
don't get confused with the concept Fragile ! in fact it results from the gross appearance of the X chromosome and is believed to be as a result of methylation / Silencing of the FMR1 gene (fragile mental Retardation gene) that would result in X-chromosome constriction at a certain point , so it would seem to be fragile at this point ! AMAZING !
what happens is that there's a trinucleotide repeat sequence of CGG codon that will expand with more than 200 repeats ! and eventually would result in silencing the gene that encodes familial mental retardation gene protein.
methylation /silencing/constriction site of X- chromosome so that it would appear as if it's fragile !
http://thebioside.ning.com/forum/topics/pre-class-ch-15-the-chromosomal-basis-for-inheritance
Mode of inheritance is X-linked DOMINANT .
characteristic appearance of this boy would be enlarged forehead "Macrosomia", elongated face, protruded jaw "prognathism", enlarged ears and testicles "Macrotia" and "Macrorchidism"
Mental retardation with liability to develop glioblastoms , ADHD is due to associated neurodegeneration of this disease.
this an Excellent link for better demonstration of this condition
http://www.gfmer.ch/genetic_diseases_v2/gendis_detail_list.php?offset=15&cat3=131
Fragile -X- Syndrome ..
don't get confused with the concept Fragile ! in fact it results from the gross appearance of the X chromosome and is believed to be as a result of methylation / Silencing of the FMR1 gene (fragile mental Retardation gene) that would result in X-chromosome constriction at a certain point , so it would seem to be fragile at this point ! AMAZING !
what happens is that there's a trinucleotide repeat sequence of CGG codon that will expand with more than 200 repeats ! and eventually would result in silencing the gene that encodes familial mental retardation gene protein.
http://thebioside.ning.com/forum/topics/pre-class-ch-15-the-chromosomal-basis-for-inheritance
Mode of inheritance is X-linked DOMINANT .
characteristic appearance of this boy would be enlarged forehead "Macrosomia", elongated face, protruded jaw "prognathism", enlarged ears and testicles "Macrotia" and "Macrorchidism"
Mental retardation with liability to develop glioblastoms , ADHD is due to associated neurodegeneration of this disease.
this an Excellent link for better demonstration of this condition
http://www.gfmer.ch/genetic_diseases_v2/gendis_detail_list.php?offset=15&cat3=131
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