Chamary and Hurst “The Price of Silent Mutations”



Chamary and Hurst “The Price of Silent Mutations”

Thesis Statement

Growing body of evidence shows that 'silent' mutations do have effects on fitness, so are not silent at all.

Introduction

Silent mutations occur when the change of a single DNA nucleotide (A, T, C, and G) within a gene does not affect the sequence of amino acids that make up the gene's protein. The sequence of amino acids determines the 3-D structure of the protein, and that determines the function of the protein in the cell, and that determines the fitness of the organism. So, if the protein is not changed it will have no effect on the phenotype and the fitness of the organism. In other words: it will be neutral. In this paper we will analyze the article “The price of silent mutations” written by Chamary and Hurst.

Analysis

Chamary and Hurst anlysed in the article “The price of silent mutations” is that silent mutations are DNA mutations that do not result in a change to the amino acid sequence of a protein. They may occur in a non-coding region (outside of a gene or within an intron), or they may occur within an exon in a manner that does not alter the final amino acid sequence. The phrase silent mutation is often used interchangeably with the phrase synonymous mutation; however, synonymous mutations are a subcategory of the former, occurring only within exons.

Because silent mutations do not alter protein function they are often treated as though they are evolutionarily neutral. However, many organisms are known to exhibit codon usage biases, suggesting that there is selection for the use of particular codons due to translational stability. Silent mutations may also affect splicing, or transcriptional control. In molecular cloning experiments, it can be useful to introduce silent mutations into a gene of interest in order to create or remove recognition sites for restriction enzymes.

Geneticists and evolutionary biologists have for decades embraced the view, no doubt reinforced by terminology such as “silent” (i.e., synonymous) mutations, that for protein-encoding genes, genotype determines phenotype through control of the amino acid sequence of the corresponding polypeptide chain or chains. In various contexts, the standard assumption has therefore been that only non-synonymous nucleotide substitutions in a gene have an impact on the phenotype and are subject to selection.

In the article Chamary and Hurst described a likely exception to the conventional wisdom ...