The serial endosymbiosis theory is a favored model for explaining the origin of mitochondria, a defining event in the evolution of eukaryotic cells. As usually described, this theory posits that mitochondria are the direct descendants of a bacterial endosymbiont that became established at an early stage in a nucleus-containing (but amitochondriate) host cell. Gene sequence data strongly support a monophyletic origin of the mitochondrion from a eubacterial ancestor shared with a subgroup of the α-Proteobacteria. However, recent studies of unicellular eukaryotes (protists), some of them little known, have provided insights that challenge the traditional serial endosymbiosis–based view of how the eukaryotic cell and its mitochondrion came to be. These data indicate that the mitochondrion arose in a common ancestor of all extant eukaryotes and raise the possibility that this organelle originated at essentially the same time as the nuclear component of the eukaryotic cell rather than in a separate, subsequent event.
Tumor necrosis factor α (TNF-α) is a cytokine with multiple roles in the immune system, including the induction and potentiation of cellular functions in neutrophils (PMNs). TNF...
A mitochondrial mutation that genetically maps in the middle of the gene coding cytochrome c oxidase subunit II has been found to be a single-base-pair deletion. Three independe...
Phylogenetic relationships, divergence times, and patterns of biogeographic descent among primate species are both complex and contentious. Here, we generate a robust molecular ...
Human genetic diversity is shaped by both demographic and biological factors and has fundamental implications for understanding the genetic basis of diseases. We studied 938 unr...
We have seen that there is no simple answer to the question ‘what controls respiration?’ The answer varies with (a) the size of the system examined (mitochondria, cell or organ)...
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