Mendelian Inheritance And Pedigrees Practice Test

A 4-year-old boy presents with progressive muscle weakness. His mother notes he has difficulty climbing stairs and frequently falls. On examination, he demonstrates a Gower sign, using his hands to push on his legs to stand up. His serum creatine kinase is significantly elevated. His mother reports that her brother is wheelchair-bound with a similar condition, Duchenne muscular dystrophy. The boy's father is healthy.

A 2-year-old boy is evaluated for recurrent pulmonary infections and failure to thrive. A sweat chloride test is markedly elevated, confirming a diagnosis of cystic fibrosis. His parents are both healthy and asymptomatic. They have an older daughter, age 4, who is also healthy. The parents deny any known family history of the disorder, but mention they are from the same small, isolated village.