INBDE (Integrated National Board Dental Examination) Practice Exam

What is the inheritance pattern of ectodermal dysplasia?

1. Autosomal dominant

2. Autosomal recessive

3. X-linked recessive

4. Mitochondrial inheritance

The correct answer is: X-linked recessive

Ectodermal dysplasia is known to follow an X-linked recessive inheritance pattern. This means that the gene causing the condition is located on the X chromosome. In X-linked recessive inheritance, males are typically more severely affected than females because they only have one X chromosome. Females can be carriers without showing the full symptoms since they have two X chromosomes. When a female carrier has a son, there is a 50% chance that he will inherit the affected X chromosome and thus be affected with the condition. Therefore, the correct answer is C, X-linked recessive. Autosomal dominant inheritance (Choice A) would require that only one copy of the gene mutation is needed to express the trait, which is not the case for ectodermal dysplasia. Autosomal recessive inheritance (Choice B) would require both parents to pass on a copy of the mutated gene, resulting in the trait, which is not the pattern for ectodermal dysplasia. Mitochondrial inheritance (Choice D) involves genes in the mitochondria and is passed on maternally, which is not the pattern seen in ectodermal dysplasia.