Abstract：
:Since the genetic code first was determined, many have claimed that it is organized adaptively, so as to assign similar codons to similar amino acids. This claim has proved difficult to establish due to the absence of relevant comparative data on alternative primordial codes and of objective measures of amino acid exchangeability. Here we use a recently developed measure of exchangeability to evaluate a null hypothesis and two alternative hypotheses about the adaptiveness of the genetic code. The null hypothesis that there is no tendency for exchangeable amino acids to be assigned to similar codons can be excluded here as expected from earlier work. The first alternative hypothesis is that any such correlation between codon distance and amino acid distance is due to incremental mechanisms of code evolution, and not to adaptation to reduce deleterious effects of future mutations. More specifically, new codon assignments that occur by ambiguity reduction or by codon capture will tend to give rise to correlations, whether due to the condition of amino acid ambiguity, or to the condition of similarity between a new tRNA synthetase (or tRNA) and its parent. The second alternative hypothesis, the adaptive hypothesis, then may be defined as an excess relative to what may be expected given the incremental nature of evolution, reflecting true adaptation for robustness rather than an incidental effect. The results reported here indicate that most of the nonrandomness in the amino acids to codon assignments can be explained by incremental code evolution, with a small residue of orderliness that may reflect code adaptation.
journal_name
J Mol Evoljournal_title
Journal of molecular evolutionauthors
Stoltzfus A,Yampolsky LYdoi
10.1007/s00239-007-9026-8subject
Has Abstractpub_date
2007-10-01 00:00:00pages
456-62issue
4eissn
0022-2844issn
1432-1432journal_volume
65pub_type
杂志文章abstract：:Oxygen-free aqueous solutions of NH4CN (0.1 M, pH9) were exposed to gamma rays from a 60Co source, the mixture of nonvolatile products was fractionated, and the fractions were analyzed. The procedures were chosen to make effective investigations of radiolytic products, and to minimize the contributions of chemical cha...
journal_title：Journal of molecular evolution
pub_type： 杂志文章
doi：10.1007/BF01732951
更新日期：1980-07-01 00:00:00
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journal_title：Journal of molecular evolution
pub_type： 杂志文章
doi：10.1007/s002390010101
更新日期：2000-10-01 00:00:00
abstract：:The helix-turn-helix domain-containing family of transcriptional regulators is of ancient origin and has been incorporated into numerous disparate biological processes. As a consequence, the forces shaping its early evolution have been difficult to reconstruct. Herein, we analyze this large and diverse family with a c...
journal_title：Journal of molecular evolution
pub_type： 杂志文章
doi：10.1007/pl00006552
更新日期：1999-09-01 00:00:00
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journal_title：Journal of molecular evolution
pub_type： 杂志文章
doi：10.1007/BF02104732
更新日期：1984-01-01 00:00:00
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journal_title：Journal of molecular evolution
pub_type： 杂志文章
doi：10.1007/s00239-006-0017-y
更新日期：2007-01-01 00:00:00
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journal_title：Journal of molecular evolution
pub_type： 杂志文章
doi：10.1007/s00239-018-9846-8
更新日期：2018-06-01 00:00:00
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journal_title：Journal of molecular evolution
pub_type： 杂志文章
doi：10.1007/BF02101000
更新日期：1986-01-01 00:00:00
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journal_title：Journal of molecular evolution
pub_type： 杂志文章
doi：10.1007/pl00006510
更新日期：1999-06-01 00:00:00
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journal_title：Journal of molecular evolution
pub_type： 杂志文章
doi：10.1007/pl00006450
更新日期：1999-02-01 00:00:00
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journal_title：Journal of molecular evolution
pub_type： 杂志文章
doi：10.1007/pl00006246
更新日期：1997-10-01 00:00:00
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journal_title：Journal of molecular evolution
pub_type： 杂志文章
doi：10.1007/BF00173155
更新日期：1995-12-01 00:00:00
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journal_title：Journal of molecular evolution
pub_type： 杂志文章
doi：10.1007/s00239-004-2596-9
更新日期：2004-06-01 00:00:00
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journal_title：Journal of molecular evolution
pub_type： 杂志文章
doi：10.1007/s00239-010-9328-0
更新日期：2010-03-01 00:00:00
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journal_title：Journal of molecular evolution
pub_type： 杂志文章
doi：10.1007/pl00006277
更新日期：1998-01-01 00:00:00
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journal_title：Journal of molecular evolution
pub_type： 杂志文章
doi：10.1007/s002390010053
更新日期：2000-06-01 00:00:00
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journal_title：Journal of molecular evolution
pub_type： 杂志文章
doi：10.1007/s002399910042
更新日期：2000-04-01 00:00:00
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journal_title：Journal of molecular evolution
pub_type： 杂志文章
doi：10.1007/pl00006406
更新日期：1998-11-01 00:00:00
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journal_title：Journal of molecular evolution
pub_type： 杂志文章
doi：10.1007/BF00182390
更新日期：1992-02-01 00:00:00
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journal_title：Journal of molecular evolution
pub_type： 杂志文章
doi：10.1007/s002390010139
更新日期：2001-02-01 00:00:00
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journal_title：Journal of molecular evolution
pub_type： 杂志文章
doi：10.1007/s00239-004-0374-3
更新日期：2005-08-01 00:00:00
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更新日期：2014-08-01 00:00:00
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doi：10.1007/s00239-004-0120-x
更新日期：2005-02-01 00:00:00
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journal_title：Journal of molecular evolution
pub_type： 杂志文章
doi：10.1007/s00239001-0052-7
更新日期：2002-04-01 00:00:00
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journal_title：Journal of molecular evolution
pub_type： 杂志文章
doi：10.1007/BF02407357
更新日期：1993-08-01 00:00:00
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journal_title：Journal of molecular evolution
pub_type： 杂志文章
doi：10.1007/BF00160400
更新日期：1994-12-01 00:00:00
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journal_title：Journal of molecular evolution
pub_type： 杂志文章
doi：10.1007/s00239-008-9149-6
更新日期：2008-12-01 00:00:00
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journal_title：Journal of molecular evolution
pub_type： 杂志文章
doi：10.1007/BF02101640
更新日期：1983-01-01 00:00:00
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journal_title：Journal of molecular evolution
pub_type： 杂志文章
doi：10.1007/s00239-004-2583-1
更新日期：2004-06-01 00:00:00
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journal_title：Journal of molecular evolution
pub_type： 杂志文章
doi：10.1007/s002390010213
更新日期：2001-09-01 00:00:00
abstract：:Here we report DNA sequences from mitochondrial cytochrome b gene segments (1,005 base pairs per species) for the extinct woolly mammoth (Mammuthus primigenius) and Steller's sea cow (Hydrodamalis gigas) and the extant Asian elephant (Elephas maximus), the Western Indian manatee (Trichechus manatus), and the hyrax (Pr...
journal_title：Journal of molecular evolution
pub_type： 杂志文章
doi：10.1007/pl00006160
更新日期：1997-04-01 00:00:00
