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Diseases » Fragile-X Syndrome » Inheritance
 

Inheritance and Genetics of Fragile-X Syndrome

Inheritance of Fragile-X Syndrome:

X-linked recessive diseases are usually inherited by males from their mother. Rare cases of sporadic genetic disease can also occur. See inheritance of x-linked recessive diseases.

Fragile-X Syndrome: Inheritance and Genetics Details

Inheritance properties of Fragile-X Syndrome:

  Disease inherited from: Usually inherited by males from their mother who is a carrier; see inheritance of x-linked recessive diseases.

  Gender bias in inheritance: Males only get x-linked recessive diseases; females are carriers.

Inheritance Patterns

Inheritance odds for Fragile-X Syndrome:

  Overall odds of inheritance: Usually inherited by males from their mother who is a carrier; see inheritance of x-linked recessive diseases.

  Sibling of diseased child odds of inheriting disease: About 50% for a second child if one (male) child already has the x-linked recessive disease.

  Mother to son inheritance odds: 50% disease, 50% disease-free, males cannot be a carrier of an x-linked recessive disease.

  Father to son inheritance odds: 0% chance usually for x-linked recessive diseases.

  Mother to daughter inheritance odds: 0% disease; 50% female carrier, 50% chance neither affected nor carrier.

  Father to daughter inheritance odds: 0% chance of x-linked recessive disease; 100% chance the female child is a carrier.

Inheritance Features

Inheritance features for Fragile-X Syndrome:

  Sporadic form of disease possible?: Yes, requires single mutation for x-linked recessive disease.

  Milder form of disease possible in females?: Yes, females have mild disease for some x-linked recessive diseases.

Fragile-X Syndrome: Genetics Information

Genetics of Fragile-X Syndrome: In normal individuals, the FMR1 gene is transmitted stably from parent to child. However, in Fragile X individuals, there is a mutation in one end of the gene (the 5' untranslated region), consisting of an amplification of a CGG repeat. Patients with fragile X syndrome have 200 or more copies of the CGG motif. The huge expansion of this repeat means that the FMR1 gene is not expressed, so no FMR1 protein is made. Although the exact function of FMR1 protein in the cell is unclear, it is known that it binds RNA. (Source: Genes and Disease by the National Center for Biotechnology)

About inheritance and genetics:

Inheritance of Fragile-X Syndrome refers to whether the condition is inherited from your parents or "runs" in families. The level of inheritance of a condition depends on how important genetics are to the disease. Strongly genetic diseases are usually inherited, partially genetic diseases are sometimes inherited, and non-genetic diseases are not inherited. For general information, see Introduction to Genetics.

 

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