Neonatal Nurse Practitioner Practice Exam

Which of the following is a characteristic of an autosomal recessive disorder?

1. It is expressed in the heterozygous state

2. Parents are phenotypically normal

3. There is a 50% risk for each offspring to be affected

4. It typically skips generations

The correct answer is: Parents are phenotypically normal

An autosomal recessive disorder is characterized by the requirement for individuals to have two copies of the recessive allele—one inherited from each parent—in order to express the disorder phenotypically. Consequently, a key feature of such disorders is that the parents of affected individuals are often phenotypically normal because they are typically carriers of the recessive allele. As carriers, these parents have one normal allele and one recessive allele, so they do not exhibit symptoms of the disorder; they can, however, pass the recessive allele to their children. Additionally, it's important to recognize that although parents may not show any signs of the disorder, there is still a chance they may have affected children if both parents contribute the recessive allele. This phenomenon is what allows the disorder to "skip generations," as the carrier status might not be apparent without further genetic testing. Understanding these nuances is crucial in identifying the inheritance patterns of autosomal recessive disorders and their implications for genetic counseling and family planning.