Which of the following is/are true regarding autosomal dominant disorders?

A. 50% of the offspring of a heterozygous single parent will manifest the disease.

B. May skip generations.

C. Expression of the clinical features is variable.

D. Do not occur due to new mutations.

E. 100% of the offspring of homozygous parents will have the disease.

Answers

A. True – In autosomal dominant disorders, a heterozygous parent (with one mutant gene and one normal gene) has a 50% chance of passing the mutant gene to each offspring, meaning 50% of the offspring will manifest the disease if they inherit the mutant gene.

B. True – Autosomal dominant disorders typically do not skip generations. If an individual inherits the mutant gene, they usually show symptoms of the disorder. However, incomplete penetrance or variable expression can sometimes give the appearance of skipping generations.

C. True – The expression of clinical features in autosomal dominant disorders can be variable. This means that the severity and specific symptoms can differ among individuals with the same disorder, even within the same family.

D. False – Autosomal dominant disorders can occur due to new mutations. These are known as de novo mutations and can happen in the germ cells of a parent or in the early development of the fertilized egg.

E. True – If both parents are homozygous (having two copies of the mutant gene), all their offspring will inherit the mutant gene and thus manifest the disease.

Note

Autosomal dominant disorders require only one copy of the mutant gene to manifest. Affected individuals usually have one affected parent.

New (de novo) mutations can cause autosomal dominant disorders, meaning the disorder can appear in a child whose parents do not have the disorder.

The severity and range of symptoms can vary widely among affected individuals, even within the same family.

Huntington’s disease, Marfan syndrome, and neurofibromatosis type 1 are common autosomal dominant disorders.