Answer:
They always represent recessively inherited disorders.
Step-by-step explanation:
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Help Me Understand Genetics
What are the different ways in which a genetic condition can be inherited?
Some genetic conditions are caused by mutations in a single gene. These conditions are usually inherited in one of several patterns, depending on the gene involved:
Patterns of inheritance
Inheritance pattern Description Examples
Autosomal dominant One mutated copy of the gene in each cell is sufficient for a person to be affected by an autosomal dominant disorder. In some cases, an affected person inherits the condition from an affected parent. In others, the condition may result from a new mutation in the gene and occur in people with no history of the disorder in their family. Huntington disease, Marfan syndrome
Autosomal recessive In autosomal recessive inheritance, both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition. Autosomal recessive disorders are typically not seen in every generation of an affected family. cystic fibrosis, sickle cell disease
X-linked dominant X-linked dominant disorders are caused by mutations in genes on the X chromosome, one of the two sex chromosomes in each cell. In females (who have two X chromosomes), a mutation in one of the two copies of the gene in each cell is sufficient to cause the disorder. In males (who have only one X chromosome), a mutation in the only copy of the gene in each cell causes the disorder. In most cases, males experience more severe symptoms of the disorder than females.
A characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons (no male-to-male transmission)
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