Autosomal dominant: autosomal dominant inheritance refers to genetic conditions that occur when a mutation is present in one copy of a given gene.

 

Autosomal recessive: autosomal recessive inheritance refers to genetic conditions that occur only when mutations are present in both copies of a given gene.

 

Mutation: a change in the usual DNA sequence at a particular gene locus.

 

Penetrance: The percentage of individuals carrying a given mutation who will manifest the disease.

 

Polymorphism: A common mutation. Polymorphisms are changes in the DNA that are most frequently non-deleterious in nature. ("Common" is typically defined as an allele frequency of at least 1%.)

 

Placebo: A pill that is given in a randomized study that has no active ingredient.

 

X-linked recessive: Refers to genetic conditions that are associated with mutations in genes on the X-chromosome. A male carrying a mutation will be affected, because he carries only one X chromosome. A female carrying a mutation in one gene, with a normal gene on the other X chromosome, will be unaffected.

 

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