Search results
Results From The WOW.Com Content Network
Point substitution mutations of a codon, classified by their impact on protein sequence. A synonymous substitution (often called a silent substitution though they are not always silent) is the evolutionary substitution of one base for another in an exon of a gene coding for a protein, such that the produced amino acid sequence is not modified.
Silent mutations, also called synonymous or samesense mutations, are mutations in DNA that do not have an observable effect on the organism's phenotype. The phrase silent mutation is often used interchangeably with the phrase synonymous mutation ; however, synonymous mutations are not always silent, nor vice versa.
Silent mutations code for the same amino acid (a "synonymous substitution"). A silent mutation does not affect the functioning of the protein. A single nucleotide can change, but the new codon specifies the same amino acid, resulting in an unmutated protein.
A nucleotide substitution at a 4-fold degenerate site is always a synonymous mutation with no change on the amino acid. [2]: 521–522 A less degenerate site would produce a nonsynonymous mutation on some of the substitutions. An example (and the only) 3-fold degenerate site is the third position of an isoleucine codon
It is calculated as the ratio of the number of nonsynonymous substitutions per non-synonymous site (K a), in a given period of time, to the number of synonymous substitutions per synonymous site (K s), in the same period. The latter are assumed to be neutral, so that the ratio indicates the net balance between deleterious and beneficial mutations.
Missense mutation is a type of nonsynonymous substitution in a DNA sequence. Two other types of nonsynonymous substitution are the nonsense mutations , in which a codon is changed to a premature stop codon that results in truncation of the resulting protein , and the nonstop mutations , in which a stop codon erasement results in a longer ...
A point substitution mutation results in a change in a single nucleotide and can be either synonymous or nonsynonymous. A synonymous substitution replaces a codon with another codon that codes for the same amino acid, so that the produced amino acid sequence is not modified. Synonymous mutations occur due to the degenerate nature of the genetic ...
The changing of a base in a codon without the changing of the translated amino acid is called a synonymous mutation. Since the amino acid translated remains the same a synonymous mutation has traditionally been considered a neutral mutation. [6] Some research has suggested that there is bias in selection of base substitution in synonymous mutation.