The review by C. William Birky, Jr. discusses the mechanisms and evolution of uniparental inheritance of mitochondrial and chloroplast genes in eukaryotes. Uniparental inheritance, where individuals inherit organelle genes from only one parent, is a widespread phenomenon in many species. The inheritance patterns can vary widely, including maternal, biparental, and paternal inheritance, depending on the species and the specific organelle. The mechanisms of uniparental inheritance are diverse, ranging from prezygotic and zygotic processes that eliminate organelles or their genomes during gametogenesis or early embryonic development. These mechanisms can be blocked by various factors, such as unequal cell division, differential growth, or random partitioning of organelles. The evolution of uniparental inheritance has been studied in a wide range of organisms, including flowering plants, green algae, fungi, and animals. Most species exhibit some degree of uniparental inheritance, with exceptions in certain yeasts and some ascomycete fungi. The evolutionary history of uniparental inheritance shows frequent reversals and parallel changes, suggesting that it is subject to varying selective pressures. The review also explores the evolutionary explanations for uniparental inheritance. One theory suggests that uniparental inheritance evolved to reduce the spread of cytoplasmic parasites or selfish organelle DNA. Another theory posits that the loss of biparental inheritance or recombination has minimal effects on natural selection, as organelle genes do not contribute significantly to linkage disequilibrium or natural selection. The maintenance of biparental inheritance and recombination may be influenced by factors such as the presence of detrimental cytoplasmic parasites, the evolution of oogamy, and the role of organelle genes in specific physiological processes. Overall, the review highlights the complexity and diversity of uniparental inheritance mechanisms and the ongoing debate about their evolutionary significance.The review by C. William Birky, Jr. discusses the mechanisms and evolution of uniparental inheritance of mitochondrial and chloroplast genes in eukaryotes. Uniparental inheritance, where individuals inherit organelle genes from only one parent, is a widespread phenomenon in many species. The inheritance patterns can vary widely, including maternal, biparental, and paternal inheritance, depending on the species and the specific organelle. The mechanisms of uniparental inheritance are diverse, ranging from prezygotic and zygotic processes that eliminate organelles or their genomes during gametogenesis or early embryonic development. These mechanisms can be blocked by various factors, such as unequal cell division, differential growth, or random partitioning of organelles. The evolution of uniparental inheritance has been studied in a wide range of organisms, including flowering plants, green algae, fungi, and animals. Most species exhibit some degree of uniparental inheritance, with exceptions in certain yeasts and some ascomycete fungi. The evolutionary history of uniparental inheritance shows frequent reversals and parallel changes, suggesting that it is subject to varying selective pressures. The review also explores the evolutionary explanations for uniparental inheritance. One theory suggests that uniparental inheritance evolved to reduce the spread of cytoplasmic parasites or selfish organelle DNA. Another theory posits that the loss of biparental inheritance or recombination has minimal effects on natural selection, as organelle genes do not contribute significantly to linkage disequilibrium or natural selection. The maintenance of biparental inheritance and recombination may be influenced by factors such as the presence of detrimental cytoplasmic parasites, the evolution of oogamy, and the role of organelle genes in specific physiological processes. Overall, the review highlights the complexity and diversity of uniparental inheritance mechanisms and the ongoing debate about their evolutionary significance.