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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.
A point mutation is a genetic mutation where a single nucleotide base is changed, inserted or deleted from a DNA or RNA sequence of an organism's genome. [1] Point mutations have a variety of effects on the downstream protein product—consequences that are moderately predictable based upon the specifics of the mutation.
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
The upper DNA molecule differs from the lower DNA molecule at a single base-pair location (a G/A polymorphism) In genetics and bioinformatics, a single-nucleotide polymorphism (SNP / s n ɪ p /; plural SNPs / s n ɪ p s /) is a germline substitution of a single nucleotide at a specific position in the genome.
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 ...
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.
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.