dorsal/arxiv
View SchemaThe Mechanisms of Codon Reassignments in Mitochondrial Genetic Codes
| Authors | Supratim Sengupta, Xiaoguang Yang, Paul G. Higgs |
|---|---|
| Categories | |
| ArXiv ID | q-bio/0703066 |
| URL | https://arxiv.org/abs/q-bio/0703066 |
| Journal | J. Mol. Evol. 64 (2007) 662-688 |
Abstract
Many cases of non-standard genetic codes are known in mitochondrial genomes. We carry out analysis of phylogeny and codon usage of organisms for which the complete mitochondrial genome is available, and we determine the most likely mechanism for codon reassignment in each case. Reassignment events can be classified according to the gain-loss framework. The gain represents the appearance of a new tRNA for the reassigned codon or the change of an existing tRNA such that it gains the ability to pair with the codon. The loss represents the deletion of a tRNA or the change in a tRNA so that it no longer translates the codon. One possible mechanism is Codon Disappearance, where the codon disappears from the genome prior to the gain and loss events. In the alternative mechanisms the codon does not disappear. In the Unassigned Codon mechanism, the loss occurs first, whereas in the Ambiguous Intermediate mechanism, the gain occurs first. Codon usage analysis gives clear evidence of cases where the codon disappeared at the point of the reassignment and also cases where it did not disappear. Codon disappearance is the probable explanation for stop to sense reassignments and a small number of reassignments of sense codons. However, the majority of sense to sense reassignments cannot be explained by codon disappearance. In the latter cases, by analysis of the presence or absence of tRNAs in the genome and of the changes in tRNA sequences, it is sometimes possible to distinguish between the Unassigned Codon and Ambiguous Intermediate mechanisms. We emphasize that not all reassignments follow the same scenario and that it is necessary to consider the details of each case carefully.
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"abstract": "Many cases of non-standard genetic codes are known in mitochondrial genomes.\nWe carry out analysis of phylogeny and codon usage of organisms for which the\ncomplete mitochondrial genome is available, and we determine the most likely\nmechanism for codon reassignment in each case. Reassignment events can be\nclassified according to the gain-loss framework. The gain represents the\nappearance of a new tRNA for the reassigned codon or the change of an existing\ntRNA such that it gains the ability to pair with the codon. The loss represents\nthe deletion of a tRNA or the change in a tRNA so that it no longer translates\nthe codon. One possible mechanism is Codon Disappearance, where the codon\ndisappears from the genome prior to the gain and loss events. In the\nalternative mechanisms the codon does not disappear. In the Unassigned Codon\nmechanism, the loss occurs first, whereas in the Ambiguous Intermediate\nmechanism, the gain occurs first. Codon usage analysis gives clear evidence of\ncases where the codon disappeared at the point of the reassignment and also\ncases where it did not disappear. Codon disappearance is the probable\nexplanation for stop to sense reassignments and a small number of reassignments\nof sense codons. However, the majority of sense to sense reassignments cannot\nbe explained by codon disappearance. In the latter cases, by analysis of the\npresence or absence of tRNAs in the genome and of the changes in tRNA\nsequences, it is sometimes possible to distinguish between the Unassigned Codon\nand Ambiguous Intermediate mechanisms. We emphasize that not all reassignments\nfollow the same scenario and that it is necessary to consider the details of\neach case carefully.",
"arxiv_id": "q-bio/0703066",
"authors": [
"Supratim Sengupta",
"Xiaoguang Yang",
"Paul G. Higgs"
],
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],
"journal_ref": "J. Mol. Evol. 64 (2007) 662-688",
"title": "The Mechanisms of Codon Reassignments in Mitochondrial Genetic Codes",
"url": "https://arxiv.org/abs/q-bio/0703066"
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