GENE20001 Lecture Notes - Lecture 10: Signal Peptide, Symbiosis, Nuclear Gene
Document Summary
Non-photosynthetic prokaryote (alpha-proteobacteria) entered ancestral eukaryote by phagocytosis. The oxidative phosphorylation activities of the ancestral eukaryote was taken over by prokaryote. Evidence for bacterial origin: reclinomonas (protozoan) has largest mt genome (97 genes), which resembles proteobacterial ancestor. There was only one mitochondrial origin: arrangement of mt ribosomal protein genes suggest mitochondria evolved only once. Notice the genes for rrna is well conserved. Tells us they"re all derived from a single ancestor. The genes that are missing have been relocated to the nuclear genome. At some point a photosynthetic prokaryote (cyanobacteria) was phagocytized. Majority (1000-1500) of proteins in mt encoded by nuclear genes. Dna polymerase, rna polymerase, translation initiation factors, ribosomal proteins, aminoacyl-trna synthetases, respiratory proteins. Rna produced by nuclear genes include 55 rrnas and 1-3 trnas. Mt genes move to the nucleus (gene transfer) Nuclear genes take over mt gene function (gene substitution) Either dna or cdna integrated into the nuclear genome but is not active.
