Single gene disorders

Lander and Schork s article was written against the backdrop of related investigations by 1990s geneticists, who also found that single-gene disorders were not so simple, even when inherited in a Mendelian way. Cystic... 

A family medical history can identify people with a higher-than-usual chance of having common disorders, such as heart disease, high blood pressure, stroke, certain cancers, and diabetes. These complex disorders are influenced by a combination of genetic factors, environmental conditions, and lifestyle choices. A family history also can provide information about the risk of rarer conditions caused by mutations in a single gene, such as cystic fibrosis and sickle cell anemia. 

Klein-Waardenburg syndrome is a single-gene disorder that includes dystopia canthorum (lateral displacement of the inner comer of the eye), impaired hearing, and pigmentary abnormalities. The gene involved is most likely to be a... 

A small sample of amniotic fluid (10-20 ml) is collected at approximately 16 weeks gestation. Fetal cells are present in the amniotic fluid and can be used to diagnose single-gene disorders, chromosome abnormalities, and some biochemical disorders. Elevated a-fetoprotein levels indicate a fetus with a neural tube defect. The risk of fetal demise because of amniocentesis is estimated to be approximately 1/200. 

As noted earlier, there are probably few single gene-associated, or monogenic, diseases and most involve a number of genes. This latter group comprises complex or multifactorial diseases, which are called QTL disorders or diseases. 

The thalassemias are the most common disorders caused by mutations of a single gene worldwide both a-thalassemia and -thalassemia occur, depending on which subunit is deficient. 

D. Pedigree analysis evaluates transmission of a single-gene disorder within a family or kindred (Figure 13-1). 

Prion diseases have attracted immense attention over the past decade, prompted, in part, by the outbreak of mad cow disease in the United Kingdom. The most common prion disease is sporadic Creutzfeldt-Jakob disease (CJD). Clinically, CJD is characterized by a rapidly progressive dementia accompanied variably by early-onset seizures, insomnia, disordered movements, and psychiatric disturbances the disease is uniformly fatal. Histochemically, the principal pathological feature of prion disease is the abnormal accumulation of an amyloid-like material composed of prion protein (PrP), which is encoded by a single gene on the short arm of chromosome 20. 

Lu Y, Kham SK, Tan PL et al. Arrayed primer extension a robust and reliable genotyping platform for the diagnosis of single gene disorders beta-thalassemia and thiopurine methyltransferase deficiency. Genet Test 2005 9 212-219. 

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