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Empirical codon substitution matrix.

Schneider A, Cannarozzi GM, Gonnet GH - BMC Bioinformatics (2005)

Bottom Line: From this data, both a probability matrix and a matrix of similarity scores were computed.They are 64 x 64 matrices describing the substitutions between all codons.Substitutions from sense codons to stop codons are not considered, resulting in block diagonal matrices consisting of 61 x 61 entries for the sense codons and 3 x 3 entries for the stop codons.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Computational Science, Swiss Federal Institute of Technology, Zurich, Switzerland. schneadr@inf.ethz.ch <schneadr@inf.ethz.ch>

ABSTRACT

Background: Codon substitution probabilities are used in many types of molecular evolution studies such as determining Ka/Ks ratios, creating ancestral DNA sequences or aligning coding DNA. Until the recent dramatic increase in genomic data enabled construction of empirical matrices, researchers relied on parameterized models of codon evolution. Here we present the first empirical codon substitution matrix entirely built from alignments of coding sequences from vertebrate DNA and thus provide an alternative to parameterized models of codon evolution.

Results: A set of 17,502 alignments of orthologous sequences from five vertebrate genomes yielded 8.3 million aligned codons from which the number of substitutions between codons were counted. From this data, both a probability matrix and a matrix of similarity scores were computed. They are 64 x 64 matrices describing the substitutions between all codons. Substitutions from sense codons to stop codons are not considered, resulting in block diagonal matrices consisting of 61 x 61 entries for the sense codons and 3 x 3 entries for the stop codons.

Conclusion: The amount of genomic data currently available allowed for the construction of an empirical codon substitution matrix. However, more sequence data is still needed to construct matrices from different subsets of DNA, specific to kingdoms, evolutionary distance or different amount of synonymous change. Codon mutation matrices have advantages for alignments up to medium evolutionary distances and for usages that require DNA such as ancestral reconstruction of DNA sequences and the calculation of Ka/Ks ratios.

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CodonPAM vs PAM and f2
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Figure 2: CodonPAM vs PAM and f2

Mentions: The relationship between CodonPAM, PAM and f2 is shown in Figure 2. It shows that amino acid PAM increases almost linearly with CodonPAM. The curve is slightly steeper for the low distances and flattens with increasing distance. The amount of synonymous substitution decays from 1 to .51 (f2 being a measure of synonymous mutation described in the Methods section).


Empirical codon substitution matrix.

Schneider A, Cannarozzi GM, Gonnet GH - BMC Bioinformatics (2005)

CodonPAM vs PAM and f2
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC1173088&req=5

Figure 2: CodonPAM vs PAM and f2
Mentions: The relationship between CodonPAM, PAM and f2 is shown in Figure 2. It shows that amino acid PAM increases almost linearly with CodonPAM. The curve is slightly steeper for the low distances and flattens with increasing distance. The amount of synonymous substitution decays from 1 to .51 (f2 being a measure of synonymous mutation described in the Methods section).

Bottom Line: From this data, both a probability matrix and a matrix of similarity scores were computed.They are 64 x 64 matrices describing the substitutions between all codons.Substitutions from sense codons to stop codons are not considered, resulting in block diagonal matrices consisting of 61 x 61 entries for the sense codons and 3 x 3 entries for the stop codons.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Computational Science, Swiss Federal Institute of Technology, Zurich, Switzerland. schneadr@inf.ethz.ch <schneadr@inf.ethz.ch>

ABSTRACT

Background: Codon substitution probabilities are used in many types of molecular evolution studies such as determining Ka/Ks ratios, creating ancestral DNA sequences or aligning coding DNA. Until the recent dramatic increase in genomic data enabled construction of empirical matrices, researchers relied on parameterized models of codon evolution. Here we present the first empirical codon substitution matrix entirely built from alignments of coding sequences from vertebrate DNA and thus provide an alternative to parameterized models of codon evolution.

Results: A set of 17,502 alignments of orthologous sequences from five vertebrate genomes yielded 8.3 million aligned codons from which the number of substitutions between codons were counted. From this data, both a probability matrix and a matrix of similarity scores were computed. They are 64 x 64 matrices describing the substitutions between all codons. Substitutions from sense codons to stop codons are not considered, resulting in block diagonal matrices consisting of 61 x 61 entries for the sense codons and 3 x 3 entries for the stop codons.

Conclusion: The amount of genomic data currently available allowed for the construction of an empirical codon substitution matrix. However, more sequence data is still needed to construct matrices from different subsets of DNA, specific to kingdoms, evolutionary distance or different amount of synonymous change. Codon mutation matrices have advantages for alignments up to medium evolutionary distances and for usages that require DNA such as ancestral reconstruction of DNA sequences and the calculation of Ka/Ks ratios.

Show MeSH