Joubert Syndrome and Related Disorders

Implications for Nurse Practitioners

Laurie Anne Ferguson, FNP-C; Maritza Salgado, FNP-BC

Disclosures

Journal for Nurse Practitioners. 2012;8(4):316-322. 

In This Article

Genetic Overview

A key factor to early identification of genetic disorders is for PCPs to have a working knowledge of inheritance patterns. Mendelian modes of inheritance include autosomal dominant, autosomal recessive, and X-linked inheritance. Autosomal dominant is a pattern in which an affected individual has 1 copy of a mutant gene and 1 normal gene on a pair of autosomal chromosomes. Individuals with autosomal dominant diseases have a 50:50 chance of passing the mutant gene and, therefore, the disorder to their children.[4]

Autosomal recessive inheritance requires 2 mutant genes for the disease to occur. The affected individual is said to be homozygous and is usually the offspring of 2 heterozygous parents. Autosomal recessive diseases are rare and often occur in the context of parental consanguinity.

X-linked inheritance refers to disorders that are caused by genes on the X sex chromosome. The Y chromosome contains only a few dozen genes; therefore, most sex-linked traits are located on the X chromosome and are said to be X-linked. Because of the presence of 1 X chromosome in males (versus 2 X chromosomes in females), males are said to be hemizygous and are more likely to inherit mutant genes carried on the X chromosome and develop the mutant phenotype. A female with 2 X chromosomes may be either heterozygous or homozygous for the mutant gene.[4]

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