altering proteins

gene mutations

- might arise during DNA replication
- they include addition, deletion, substitution, inversion, duplication and translocation of bases
- occur spontaneously
- the mutation rate is increased by mutagenic agents
- mutations can result in a different amino acid sequence in the encoded polypeptide
- some gene mutations change only one triplet code

mutation

change in the DNA base sequence

substitution mutation

a base is replaced with another base

deletion mutation

frameshift: change in the reading frame

possible effects of gene mutations

non-sense, mis-sense, silent

non-sense

stop codon created - non-functional protein

mis-sense

different amino acid is coded for - different functional protein

silent

same amino acid is coded for - because the code is degenerate