what is a silent mutation?

Question

is it a change in DNA sequence but no change in protein sequence, or is it a change in genotype but no change in phenotype?

Answer 1

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. An online tool that can analyse a sequence of interest for possible mutations to create restriction sites is given in the External Links section.

Recent results suggest that silent mutations can have an effect on subsequent protein structure and activity[1],[2].


[edit] References
^ http://www.sciencemag.org/cgi/content/full/315/5811/466
^ http://sciencenow.sciencemag.org/cgi/content/full/2006/1222/2
Chao HK, Hsiao KJ, Su TS (2001). "A silent mutation induces exon skipping in the phenylalanine hydroxylase gene in phenylketonuria". Hum Genet 108 (1): 14-9. PMID 11214902.
Montera M, Piaggio F, Marchese C, Gismondi V, Stella A, Resta N, Varesco L, Guanti G, Mareni C (2001). "A silent mutation in exon 14 of the APC gene is associated with exon skipping in a FAP family". J Med Genet 38 (12): 863-7. PMID 11768390. Full text
Chava Kimchi-Sarfaty, Jung Mi Oh, In-Wha Kim, Zuben E. Sauna, Anna Maria Calcagno, Suresh V. Ambudkar, Michael M. Gottesman (2007). "A "Silent" Polymorphism in the MDR1 Gene Changes Substrate Specificity". Science 315: 525-528. Abstract Summary Full Text

Answer 2

Genotype change but hardly a phenotype change.

A silent mutation is NOT caused by a change in the amino acid sequence of the protein, which can occur any where on the DNA strand. It can cause a change in the genotype, or no change at all (if it happens in an inactive intron).

It is possible for a silent mutation to affect a phenotype, but unlikely; because a phenotype is a trait that is not genetic, but can be inherited; like instincts.

According to Wikipeida: http://en.wikipedia.org/wiki/Silent_mutation
"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. An online tool that can analyse a sequence of interest for possible mutations to create restriction sites is given in the External Links section."

According to Wikipeida: http://en.wikipedia.org/wiki/Phenotype
"A phenotype describes any observed quality of an organism, such as its morphology, development or behaviour, as opposed to its genotype- the inherited instructions it carries which may or may not be expressed. This genotype-phenotype distinction was proposed by Wilhelm Johannsen in 1911 to make clear the difference between an organism's heredity and what that heredity produces."

Answer 3

RE:
what is a silent mutation?
is it a change in DNA sequence but no change in protein sequence, or is it a change in genotype but no change in phenotype?

Answer 4

I'm guessing a change in genotype but not phenotype