This thesis provides a comprehensive review of mitochondrial DNA (mtDNA), elucidating its unique structure, encoding capabilities, and the implications of mtDNA mutations for mitochondrial diseases. Mitochondria, critical for cellular energy production, house a compact and efficient genome that is remarkable for its polycistronic nature and lack of introns, emphasizing the organelle's role as the cell's powerhouse. A significant focus is placed on the susceptibility of mtDNA to mutations due to its proximity to the electron transport chain and lack of histone protection, which predisposes it to a higher mutation rate compared to nuclear DNA. These mutations are intricately linked to a spectrum of mitochondrial disorders, ranging from neurodegenerative diseases to metabolic dysfunctions and aging. The thesis delves into the concept of heteroplasmy and its impact on the clinical manifestation of mitochondrial diseases, alongside the unique maternal inheritance pattern that adds complexity to the diagnosis and management of these conditions. The review extends to primary mitochondrial disorders (MIDs), emphasizing their prevalence and the diversity of clinical manifestations that complicate diagnosis and treatment. Notable conditions such as Leber Hereditary Optic Neuropathy (LHON), Leigh Syndrome, and Mitochondrial Neurogastrointestinal Encephalomyopathy (MNGIE) are examined to illustrate the varied impact of mitochondrial dysfunction. Therapeutic strategies for mitochondrial diseases are critically assessed, from traditional symptomatic treatments to emerging approaches like gene therapy and mitochondrial replacement therapy, highlighting the advances and challenges in developing effective treatments. The thesis also explores the role of genetic counseling and reproductive options in managing mitochondrial diseases, considering the complex inheritance patterns and the potential of mitochondrial donation techniques to prevent disease transmission.