gene expression mutations

Mutation

Permanent change to the base sequence of an organism’s DNA.

Redundancy of the code

There are 64 possible codons and only 20 different amino acids. Thus, some codons code for the same amino acid.

Missense Mutation

A gene mutation where a single nucleotide change results in a codon that codes for a different amino acid.

Same-sense Mutation

A base substitution altering one of the codons, but does not have affect on the resulting amino acid sequence.

Nonsense Mutation

A gene mutation where a single nucleotide change causes a STOP codon, which does not code for an amino acid.

→ results in the premature termination of translation.

→ polypeptide chain will be incomplete and will not fold up into a functional protein.

Reading Frameshifts

Base insertions and deletions will disrupt the reading frame, as the genetic code is read in 3s.

• every downstream triplet is affected and all forward codons, along with the amino acid they code for are altered.