MEDizzy - A 4-year-old child is referred by the pediatrician to a

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NUCLEIC ACID

A 4-year-old child is referred by the pediatrician to a pediatric neurologist after presenting with myoclonic seizures and lactic acidosis. The neurologist orders a muscle biopsy, and the pathology returns with the appearance of ‘‘ragged red fibers.’’ The parents are informed that the child has MERFF syndrome, a mitochondrial DNA (mtDNA) disorder. Which of the following statements best explains mtDNA?

ExplanationMitochondrial DNA is a small double-stranded circular DNA. It is inherited exclusively from the mother because the ovum contributes the cytoplasm to the zygote, which contains all the mitochondria for the zygote. The mitochondrial DNA replication machinery is less evolved than nuclear DNA and replicates with an error rate that is 5 to 10 times greater than that of the nuclear genome. The genetic code within mitochondria is slightly different than that of the nuclear genome