This document discusses organelle genomes, focusing on chloroplast and mitochondrial DNA. It provides details on the structure and content of chloroplast genomes, noting they typically contain 110-120 genes and are characterized by inverted repeats and single copy regions. Mitochondrial genomes are more variable in content and size. The structure and replication of human mitochondrial DNA is described in detail, including its circular nature and asymmetric replication process. Mitochondrial DNA mutations can cause a range of neuromuscular diseases due to mitochondrial dysfunction.