**Core Concept:** Myotonic dystrophy is a genetic disorder caused by mutations in the DMPK, CNBP, or ZNF9 genes, leading to the accumulation of CTG trinucleotide repeats in the DNA sequence. The disease is characterized by muscle weakness, wasting, and susceptibility to cataract formation.

**Why the Correct Answer is Right:** Myotonic dystrophy is inherited in a **dominant pattern** with incomplete penetrance, meaning that affected individuals have one normal and one mutated allele, but not all individuals with a mutated allele will develop the disease. The disease is caused by mutations in the DMPK, CNBP, or ZNF9 genes, which are located on autosomes, not chromosomes X or Y.

**Why Each Wrong Option is Incorrect:**

A. Dominant inheritance (option A) is incorrect because the disease is inherited in a dominant pattern with incomplete penetrance, not autosomal dominant inheritance.
B. Autosomal recessive inheritance (option B) is incorrect because the disease is inherited in a dominant pattern, not a recessive pattern.
C. X-linked inheritance (option C) is incorrect because the disease is inherited in a dominant pattern and affects both males and females, unlike X-linked disorders which are always inherited in a recessive pattern and affect males more severely than females.
D. Mitochondrial inheritance (option D) is incorrect because the disease is caused by mutations in nuclear genes (DMPK, CNBP, or ZNF9) and not mitochondrial DNA.

**Clinical Pearl:** Understanding the inheritance pattern of myotonic dystrophy is crucial for genetic counseling, as it affects both males and females equally, and the penetrance is incomplete, meaning that not all individuals with a mutated gene will develop the disease. This understanding can help in predicting the risk of the disease in offspring and guiding genetic testing for family members.