How Does Someone Get Rett Syndrome?

How Do People Get Rett Syndrome?
       More than 99% of people with Rett syndrome have no family history of the disorder and the condition  is not inherited because Rett syndrome results from a genetic mutation of the MECP2 gene, but there have been cases in which there has been a history of Rett syndrome within the family. Cases in which there has been a history of Rett syndrome within the family has helped researchers of the disorder discover that the cause of the disorder and its variants have an X-linked dominant pattern of inheritance. A genetic condition is considered X-linked if the mutated gene that caused the disorder is located on the X chromosome, and the inheritance occurs, if it is dominant, when one copy of the altered gene in each cell is sufficient enough to cause the condition.
        Males with mutations in the MECP2 gene usually die in infancy because the Y chromosome is too small to support life with a dysfunctional partner chromosome, but a small portion of males with a genetic mutation Involving MECP2 have exhibited signs of Rett syndrome, such as intellectual' disability, seizures, and movement dysfunctions, which is known as neonatal encephalopathy.
Genotypes of Parents Whose Offspring had Rett Syndrome
       DNA extracted from patients who had Rett syndrome and DNA extracted from the parents showed that the patient had one paternal and one maternal allele, which is normal, so researchers delved deeper in to the mystery. Single nucleotide polymorphisms (SNPs) are variations in the DNA code that are unique to individuals, much like finger prints, so if the patient had only one copy of an SNP within the MECP2 gene, then researchers could look at the parents' DNA to discover the same SNP present within their genes also present n their child's, thus allowing scientists to find the origin of the patient's alleles and thus the origin of the mutation. After all of the data, researchers concluded that, although Rett syndrome only affects women, parental genes are at the origin of Rett syndrome IN MOST CASES.
Chances of Rett Syndrome Being Passed Down to Offspring
       A parent with a small portion of mutated cells with a Rett syndrome mutation, while not exhibiting Rett syndrome, will pass these genes to their child and all of the child's cells will be mutated, resulting in Rett syndrome. People who have a small portion of their cells mutated while not exhibiting a genetic disorder or abnormality are called "mosaicism". People who have Rett syndrome and have children do not always produce children with Rett syndrome, but there is a 50% chance to pass the disorder on to the child during pregnancy. If the child is male, the Rett syndrome exhibited in the male will ne extreme. Most people-women-with Rett syndrome do not have children.

For more information, please visit:
- http://www.ghr.nlm.nih.gov/condition/rett-syndrome
- http://www.rett.childhealthresearch.org.au/our-research/research-snapshots/zhang-parental-origin-of-mutations.aspx
-http://www.elcaminogmi.dnadirect.com/gcr/patient-site/rett-syndrome-diagnosis/genetics-of-rett-syndrome.html