North American Registry of Midwives (NARM) Practice Exam

Cystic fibrosis, sickle cell anemia, and Tay-Sachs disease are examples of which category of disorders?

1. X-linked disorders

2. Autosomal dominant disorders

3. Autosomal recessive disorders

4. Chromosomal disorders

The correct answer is: Autosomal recessive disorders

Cystic fibrosis, sickle cell anemia, and Tay-Sachs disease are categorized as autosomal recessive disorders. This classification means that for a person to be affected by one of these conditions, they must inherit two copies of the mutated gene—one from each parent. In the case of cystic fibrosis, the disorder is caused by mutations in the CFTR gene, leading to the production of thick, sticky mucus that can cause severe respiratory and digestive problems. Sickle cell anemia results from a mutation in the HBB gene, which affects hemoglobin and leads to distorted red blood cells, causing various health complications. Tay-Sachs disease is caused by a deficiency in the HEXA gene, leading to the accumulation of toxic substances in the brain that ultimately causes neurodegeneration. These disorders demonstrate characteristics typical of autosomal recessive inheritance, including their equal prevalence in males and females and the requirement for both parents to be carriers for their offspring to be affected. When only one copy of the mutated gene is inherited, the individual typically remains asymptomatic but can pass the gene to the next generation. This contrasts with autosomal dominant disorders, where only one mutated copy can cause the disease, and X-linked disorders, which are linked to genes on the