What are silent mutations, sense, and misssense mutations?

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jerichorayel eNotes educator| Certified Educator

Silent, nonsense and missense mutations are DNA point mutations that affects a small gene or the nucleotide which is due to malfunction of DNA replication or exchange of nucleotides of other nucleotides within the genetic component. The changes in the nucleotides may affect the transcription and coding of right proteins thus can affect the metabolic activity of the affected individual. 

Silent - is the mutation that happens when a particular nucleotide is altered with another nucleotide but does not affect the coded protein. Meaning, the altered nucleotide will still code for the same amino acid. For example, GUU, GUC, GUA and GUG all code for the amino acid valine. Let's say a sequence GUC is altered where in C is replaced with an A. The amino acid will still be valine since GUC and GUA code for valine. 

Nonsense - The altered nucleotide is a code for a stop thus can cut the production of the peptide or protein. The codes for stop codon are UAA, UAG, and UGA. One code for glycine is GGA, when the first G is altered with a  U, the process will stop and the production of protein will be truncated. 

Missense - the altered nucleotide code for a different amino acid. Let's use valine's code again. If GUU is altered to GGU, glycine will be produced instead. 

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