Title: Inheritance of Single-Gene Disorders - Fundamentals - Merck Manuals Consumer Version
Headings: Inheritance of Single-Gene Disorders
Inheritance of Single-Gene Disorders
Penetrance and expressivity
How Genes Affect People: Penetrance and Expressivity
Inheritance Patterns
Examples of Genetic Disorders
Non–X-Linked (Autosomal) Inheritance
Dominant disorders
Recessive disorders
Non–X-Linked (Autosomal) Recessive Disorders
X-Linked Inheritance
Dominant disorders
Recessive disorders
X-Linked Recessive Disorders
Sex-Limited Inheritance
Abnormal Mitochondrial Genes
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Content: In such cases, patterns can be identified based on whether the trait is dominant or recessive, and whether the gene is X-linked or carried on the mitochondrial genome. Table
Examples of Genetic Disorders
Examples of Genetic Disorders
Gene
Dominant
Recessive
Non–X-linked (autosomal)
Marfan syndrome
Huntington disease
Cystic fibrosis
X-linked
Familial rickets
Hereditary nephritis
Red–green color blindness
Hemophilia
Non–X-Linked (Autosomal) Inheritance
Non-X-linked genes are genes carried on one or both of the 22 pairs of nonsex (autosomal) chromosomes. Dominant disorders
The following principles generally apply to dominant disorders determined by a dominant non–X-linked gene: When one parent has the disorder and the other does not, each child has a 50% chance of inheriting the disorder. People who do not have the disorder usually do not carry the gene and thus do not pass the trait on to their offspring. Males and females are equally likely to be affected. Most people with the disorder have at least one parent with the disorder, although the disorder may not be obvious and may even have been undiagnosed in the affected parent. However, sometimes the disorder arises as a new genetic mutation. Recessive disorders
The following principles generally apply to recessive disorders determined by a recessive non–X-linked gene: Virtually everyone with the disorder has parents who both carry a copy of the abnormal gene, even though usually neither parent has the disorder (because two copies of the abnormal gene are necessary for the gene to be expressed).