Prokaryotic photosynthetic organisms do not have chloroplasts.
The archezoan scenario is closest to the classical endosymbiont hypothesis of mitochondrial evolution. The basic difference between the two scenarios is if the alpha-proteibacterial emdosybiosis that produced the proto-mitichondrion was simultaneous to the formation of the eukaryotic cell, like in the symbiosis scenario, or the primitive amitochondriate cell, like in the archezoan scenario.
It lacks the introns present in corresponding genomic DNA.
The protein synthesis of these organelles is semi-independent of thatoccurring in the cytoplasm and it is inhibited by the same antibiotic thatworks on prokaryotes.
The endosymbiotic hypothesis was popularized by . In her 1981 work she argued that eukaryotic cells originated as communities of interacting entities, including endosymbiotic that developed into eukaryotic and . This last idea has not received much acceptance, since flagella lack DNA and do not show ultrastrucural similarities to prokaryotes. According to Margulis and Sagan (1996), "Life did not take over the globe by combat, but by networking" (i.e., by cooperation), and Darwin's notion of evolution driven by competition is incomplete. However, others have argued that endosymbiosis involves rather than mutualism.
Frequentlyused in phylogenetics and computational biology.
Expanded genome/proteome databases and effective use of sequence alignment tools make it possible to trace the phylogeny of individual eukaryotic proteins and ultimately to identify the prokaryotes that contributed to the last eukaryotic common ancestor (LECA). I developed an application of reciprocal BLASTp that identifies (1) the prokaryotic lineages that have contributed to the nuclear genome and (2) the specific proteins acquired from prokaryotic ancestors. Eight complete eubacterial proteomes were analyzed: two free-living spirochetes, two clostridia, two actinobacteria, and two proteobacteria (one alpha and one gamma). The data reveal a spirochete genetic contribution to the eukaryotic genome including essential proteins involved in DNA binding and repair, cyclic nucleotide metabolism, acyltransferase, and signal transduction. My results, consistent with the sulfur syntrophy hypothesis that posits LECA evolved from a merger of spirochetes (eubacteria) with sulfidogenic eocytes (archaebacteria), confirm the contribution of mitochondrial genes from alpha-proteobacteria. A contribution from clostridia to eukaryote genomes was also detected whereas none was seen from either actinobacterium or Escherichia coli. The complete spirochete and clostridial genetic contributions to eukaryotes and those of other eu-and archaebacteria can be identified by this method.
When the cell has a proper nucleus (eu-karyon), it is .
A 16kb mitochondrial genome from several mammalian species was completely sequenced to reveal the genetic function of mitochondria DNA (mtDNA). This showed that mtDNA encodes a small number of protein subunits. Further investigations of mtDNA from non-animal species showed that mtDNA held a higher coding capacity as well ass variation in size, physical form, organizational patterns and modes of expression. There are additional respiratory and ribosomal proteins encoded within mtDNA. Research has also shown that some mitochondrial genomes have decreased in size, losing many of the encoded proteins in the process.
It has most advantages of a prokaryotic system but is atrue .
Biologist Lynn Margulis first made the case for endosymbiosis in the 1960s, but for many years other biologists were skeptical. Although Jeon watched his amoebae become infected with the x-bacteria and then evolve to depend upon them, no one was around over a billion years ago to observe the events of endosymbiosis. Why should we think that a mitochondrion used to be a free-living organism in its own right? It turns out that many lines of evidence support this idea. Most important are the many striking similarities between prokaryotes (like bacteria) and mitochondria: