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15. Beskrive hvordan mutationer kan resultere i ukorrekte proteinstrukturer
Devlin, s.238-9

Mutation – a change in a gene. Mutations happen on DNA level, and can be caused by a replication error, damage to the DNA or errors during repair of the damage. The DNA is then transcribed to mRNA and in the end result in a wrong amino acid sequence in proteins.

Point mutations are changes in a single base pair in DNA, thus in mRNA.

Silent mutations – a change in a single base pair occurs in the third position of a degenerated codon. The resulting protein is completely normal, since the same specific amino acid is incorporated in the growing polypeptide chain.  

Missence mutations – a change in a single base results in incorporation of a wrong amino acid. This mutation can also be in the third position of the codon, but the codon in that case is no degenerated. The created protein is not functioning completely, but normal amounts of the protein are still found in the cell.

Nonsense mutation - a type of a missence mutation, in which the point mutation transforms an amino acid codon into a stop codon or v.v. The result is, respectively a shorter or a longer protein. The translation of the longer protein goes on until a new termination codon is reached. The finished protein is completely not functioning.

Frameshift mutation – an insertion or deletion of a single base pair (due to intercalated molecules or inverted repeats in the DNA) changes completely the reading frame resulting in a completely wrong protein, often prematurely terminated because a stop codon is reached.

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