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  • Mitochondria  (5)
  • Directional mutation pressure  (2)
  • AT/GC pressure  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Evolution of the mitochondrial genetic code IV. AAA as an asparagine codon in some animal mitochondria (1990)
    Springer
    Journal of molecular evolution 30 (1990), S. 329-332 
    Details
    ISSN: 1432-1432
    Keywords: Genetic code ; Mitochondria ; Echinoderms ; Platyhelminth ; Fasciola
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Differences in assignments from those in the universal genetic code occur in codes of mitochondria. In this report, the published sequences of the mitochondrial genes for COI and ND1 in a platyhelminth (Fasciola hepatica) are examined and it is concluded that AAA may be a codon for asparagine instead of lysine, whereas AAG is the sole codon for lysine in this species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02101887
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  • 2
    Electronic Resource
    Electronic Resource
    Amino acid codes in mitochondria as possible clues to primitive codes (1981)
    Springer
    Journal of molecular evolution 18 (1981), S. 15-17 
    Details
    ISSN: 1432-1432
    Keywords: Amino acid code ; Evolution ; Primitive codes ; Mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Differences between mitochondrial codes and the universal code indicate that an evolutionary simplification has taken place, rather than a return to a more primitive code. However, these differences make it evident that the universal code is not the only code possible, and therefore earlier codes may have differed markedly from the previous code. The present universal code is probably a “frozen accident.” The change in CUN codons from leucine to threonine (Neurospora vs. yeast mitochondria) indicates that neutral or near-neutral changes occurred in the corresponding proteins when this code change took place, caused presumably by a mutation in a tRNA gene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01733206
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  • 3
    Electronic Resource
    Electronic Resource
    Evolution of the mitochondrial genetic code I. Origin of AGR serine and stop codons in metazoan mitochondria (1989)
    Springer
    Journal of molecular evolution 29 (1989), S. 202-207 
    Details
    ISSN: 1432-1432
    Keywords: Genetic code ; Codon (capture) reassignment ; Arginine codons ; Serine codons ; AGR stop codons ; Mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary AGA and AGG (AGR) are arginine codons in the universal genetic code. These codons are read as serine or are used as stop codons in metazoan mitochondria. The arginine residues coded by AGR in yeast orTrypanosoma are coded by arginine CGN throughout metazoan mitochondria. AGR serine sites in metazoan mitochondria are occupied mainly in corresponding sites in yeast orTrypanosoma mitochondria by UCN serine, AGY serine, or codons for amino acids other than serine or arginine. Based on these observations, we propose the following evolutionary events. AGR codons became unassigned because of deletion of tRNA Arg (UCU) and elimination of AGR codons by conversion to CGN arginine codons. Upon acquisition by serine tRNA of pairing ability with AGR codons, some codons for amino acids other than arginine mutated to AGR, and were caputed by anticodon GCU in serine tRNA. During vertebrate mitochondrial evolution, AGR stop codons presumably were created from UAG stop by deletion of the first nucleotide U and by use of R as the third nucleotide that had existed next to the ancestral UAG stop.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02100203
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  • 4
    Electronic Resource
    Electronic Resource
    Codon reassignment (codon capture) in evolution (1989)
    Springer
    Journal of molecular evolution 28 (1989), S. 271-278 
    Details
    ISSN: 1432-1432
    Keywords: Genetic code ; Codon reassignment ; Codon capture ; Directional mutation pressure ; AT/GC pressure ; Wobble rules ; Mitochondria ; Mycoplasma ; Ciliated protozoa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The genetic code, once thought to be “frozen”, show variations from the universal code. Variations are found in mitochondria,Mycoplasma, and ciliated protozoa. The variations results from reassignment of codons, especially stop codons. The ressignments take place by disappearance of a codon from coding sequences, followed by its reappearance in a new role. Simultaneously, a changed anticodon must appear. We discuss the role of directional mutation pressure in the pressure in the events, and we also describe the possibility that such events have taken place during early evolution of the genetic code and can occur during its present evolution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02103422
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  • 5
    Electronic Resource
    Electronic Resource
    A comparison of mitochondrial tRNAs in five vertebrates (1995)
    Springer
    Journal of molecular evolution 40 (1995), S. 537-540 
    Details
    ISSN: 1432-1432
    Keywords: Transfer RNA ; Mitochondria ; Neutral changes ; Evolutionary divergence ; Vertebrates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Sequences of several vertebrate mitochondrial tRNAs were aligned and compared. The comparisons were made in pairs of the tRNAs for an identical amino acid. There are 22 genes for different tRNAs in each vertebrate mitochondrial DNA. The closest similarities were between rat and mouse, the next were between mammals, and the widest difference was between human or rat and Xenopus laevis. However, there were very wide variations between different amino acids in each set of comparisons. The time lapse for each percent of difference greatly increased with evolutionary separation. Most of the nucleotide substitutions appeared to be neutral in character.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00166622
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  • 6
    Electronic Resource
    Electronic Resource
    Relationship between G + C in silent sites of codons and amino acid composition of human proteins (1993)
    Springer
    Journal of molecular evolution 36 (1993), S. 201-213 
    Details
    ISSN: 1432-1432
    Keywords: G + C content ; Silent sites ; GC pressure ; Directional mutation pressure ; Human genome ; Codon usage ; Amino acid composition ; Neutral theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have investigated the relationship between the G + C content of silent (synonymous) sites in codons and the amino acid composition of encoded proteins for approximately 1,600 human genes. There are positive correlations between silent site G + C and the proportions of codons for Arg, Pro, Ala, Trp, His, Gln, and Leu and negative ones for Tyr, Phe, Asn, Ile, Lys, Asp, Thr, and Glu. The median proteins coded by groups of genes that differ in silent-site G + C content also differ in amino acid composition, as do some proteins coded by homologous genes. The pattern of compositional change can be largely explained by directional mutation pressure, the genetic code, and differences in the frequencies of accepted amino acid substitutions; the shifts in protein composition are likely to be selectively neutral.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00160475
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