Question

A 10-year-old girl is diagnosed with Marfan syndrome, an autosomal dominant condition. An extensive review of her pedigree indicates no previous family history of this disorder. The most likely explanation for this pattern is

A. highly variable expression of the disease phenotype
B. incomplete penetrance
C. mitochondrial compensation in the mother
D. new mutation transmitted by one of the parents to the affected girl
E. pleiotropy

Answer 1

The most likely explanation for a 10-year-old girl with no prior family history being diagnosed with Marfan syndrome, an autosomal dominant condition, is a new mutation passed on by one of the parents.

Step-by-step explanation:

The most likely explanation for the pattern of inheritance observed in a 10-year-old girl diagnosed with Marfan syndrome without a previous family history of this disorder is a new mutation transmitted by one of the parents to the affected girl. Marfan syndrome is an autosomal dominant condition, which means that the presence of just one faulty gene can cause the disease. In the case of autosomal dominant disorders, both males and females have an equal chance of inheritance and displaying the phenotype. A new mutation could have occurred in the parental germ cell, leading to the affected child without any prior family history of the condition.