beta thalassemia is the  most common autosomal recessive disorder. the present study reports a rare β globin gene mutation, hbb: c.180g>a: codon 59 (aag/aaa), in a patient from gilan province, northern iran. nucleotide sequencing of amplified dna belonging to a 35 years old man presenting mild hypochromia revealed a synonymous mutation due to a g>a conversion at the third position of codon 59 o...

Codon-and amino acid-substitution models are widely used for the evolutionary analysis of protein-coding DNA sequences. Using codon models, the amounts of both nonsynonymous and synonymous DNA substitutions can be estimated. The ratio of these amounts represents the strength of selective pressure. Using amino acid models, the amount of nonsynonymous substitutions is estimated, but that of synon...

Evolution of protein sequences is largely governed by purifying selection, with a small fraction of proteins evolving under positive selection. The evolution at synonymous positions in protein-coding genes is not nearly as well understood, with the extent and types of selection remaining, largely, unclear. A statistical test to identify purifying and positive selection at synonymous sites in pr...

MOTIVATION A codon position could perform different or multiple roles in alternative transcripts of a gene. For instance, a non-synonymous position in one transcript could be a synonymous site in another. Alternatively, a position could remain as non-synonymous in multiple transcripts. Here we examined the impact of codon position plurality on the frequency of deleterious single-nucleotide vari...

Recent large-scale genomic and evolutionary studies have revealed the small but detectable signature of weak selection on synonymous mutations during mammalian evolution, likely acting at the level of translational efficacy (i.e., translational selection). To investigate whether weak selection, and translational selection in particular, plays any role in shaping the fate of synonymous mutations...

ascribed to single nucleotide polymorphism (SNP) allelic variants that occur at a frequency of .1% (Ref. 1). Owing to the application of high-throughput SNP detection techniques, the number of identified SNPs is growing rapidly, enabling detailed statistical studies2–5. These include studies of SNPs that affect the amino acid sequence of a gene product (non-synonymous SNPs); they complement the...

This study examined polymorphisms in the dihydrofolate reductase (DHFR) gene of Pneumocystis carinii isolates from 27 patients with P. carinii pneumonia (PCP) in Japan. Four substitution sites with two synonymous and two non-synonymous changes were found. Two synonymous substitutions at nucleotide positions 540 and 312 were identified in one and 13 patients, respectively. Two amino acid substit...

We have used analysis of variance to partition the variation in synonymous and amino acid substitution rates between three effects (gene, lineage, and a gene-by-lineage interaction) in mammalian nuclear and mitochondrial genes. We find that gene effects are stronger for amino acid substitution rates than for synonymous substitution rates and that lineage effects are stronger for synonymous subs...

Synonymous rare codons are considered to be sub-optimal for gene expression because they are translated more slowly than common codons. Yet surprisingly, many protein coding sequences include large clusters of synonymous rare codons. Rare codons at the 5' terminus of coding sequences have been shown to increase translational efficiency. Although a general functional role for synonymous rare cod...

Although changes in nucleotide sequence affecting the composition and the structure of proteins are well known, functional changes resulting from nucleotide substitutions cannot always be inferred from simple analysis of DNA sequence. Because a strong synonymous codon usage bias in the human DRD2 gene, suggesting selection on synonymous positions, was revealed by the relative independence of th...