Type of inheritance in MELAS?
**Core Concept**
MELAS syndrome is a mitochondrial disorder characterized by **mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes**. The underlying principle being tested is the mode of inheritance of mitochondrial diseases. Mitochondrial DNA is inherited solely from the mother.
**Why the Correct Answer is Right**
MELAS syndrome is caused by mutations in mitochondrial DNA. Since mitochondrial DNA is maternally inherited, all offspring of an affected mother can inherit the mutation, but only females can pass it on to their children. This pattern is consistent with **mitochondrial inheritance**.
**Why Each Wrong Option is Incorrect**
**Option A:** Autosomal dominant inheritance does not apply as MELAS is not inherited from fathers.
**Option B:** Autosomal recessive inheritance is incorrect because MELAS does not require both parents to be carriers.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that mitochondrial diseases like MELAS exhibit **maternal inheritance**, affecting both males and females but only passed on by females.
**Correct Answer:** D. Mitochondrial inheritance.