Heterogeneity in Codon Usage in the Flatworm Schistosoma mansoni |
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Authors: | Héctor Musto Héctor Romero Helena Rodríguez-Maseda |
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Institution: | (1) Sección Bioquímica, Facultad de Ciencias, Tristán Narvaja 1674, Montevideo 11200, Uruguay, UY;(2) Departamento de Genética, Facultad de Medicina, Av. Gral. Flores 2125, Montevideo 11800, Uruguay, UY |
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Abstract: | Synonymous codon choices vary considerably among Schistosoma mansoni genes. Principal components analysis detects a single major trend among genes, which highly correlates with GC content in
third codon positions and exons, but does not discriminate among putatively highly and lowly expressed genes. The effective
number of codons used in each gene, and its distribution when plotted against GC3, suggests that codon usage is shaped mainly by mutational biases. The GC content of exons, GC3, 5′, 3′, and flanking (5′+ 3′+ introns) regions are all correlated among them, suggesting that variations in GC content may
exist among different regions of the S. mansoni genome. We propose that this genome structure might be among the most important factors shaping codon usage in this species,
although the action of selection on certain sequences cannot be excluded.
Received: 10 March 1997 / Accepted: 27 June 1997 |
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Keywords: | : Genome organization — Isochores — Base composition — Effective number of codons — Platyhelminthes — Schistosoma mansoni |
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