**Question:** Werner syndrome is

A. Autosomal recessive disorder
B. X-linked dominant disorder
C. X-linked recessive disorder
D. Mitochondrial disorder

**Core Concept:** Werner syndrome is a rare genetic disorder characterized by premature aging. It is caused by mutations in the WRN gene, which encodes a protein involved in DNA repair and recombination. This protein deficiency leads to genomic instability, telomere shortening, and cellular senescence.

**Why the Correct Answer is Right:** Werner syndrome is an autosomal recessive disorder, meaning it is inherited when both parents pass on a mutated copy of the WRN gene. In this case, the correct answer is A.

**Why Each Wrong Option is Incorrect:**

B. X-linked dominant disorders are inherited when an affected parent passes on the mutated gene to their offspring. Since Werner syndrome is autosomal recessive, option B is incorrect.

C. X-linked recessive disorders are inherited when an affected parent passes on the mutated gene to their offspring. Since Werner syndrome is autosomal recessive, option C is incorrect.

D. Mitochondrial disorders are caused by mutations in mitochondrial DNA or nuclear genes that affect mitochondrial function. Werner syndrome is a nuclear gene disorder, so option D is incorrect.

**Clinical Pearl:** Werner syndrome patients present with a range of clinical features, including premature graying of hair, balding, and short stature. They often develop diabetes, hypertension, and osteoporosis, which are not specific to mitochondrial disorders.

**Correct Answer:** Werner syndrome is an autosomal recessive disorder (option A).