8.1 Alteration of sequence of bases in DNA can altar the structure of proteins

What happens in substitution a mutation

A single nucleotide base is exchanged for another

What happens in an addition mutation

one or more nucleotide bases are added to the base sequence

What happens in a deletion mutation

one or more nucleotide bases are removed from the base sequence

What happens in an inversion mutation

a group of bases become separated from the DNA sequence and re-join in the same position but in inverse order

What happens in a translocation mutation

a group of bases become separated from the DNA sequence on one chromosome and become inserted into the DNA sequence of a different chromosome

What happens in a duplication mutation

one ore more bases are duplicated/repeated in the DNA sequence

how can mutations occur spontaneously

During replication mutations can occur randomly and spontaneously

natural mutation rate is around 1 to 2 genes per 100000 per generation

how can you increase the rate of mutation

The rate can be increased by ionising radiation such as UV radiation or chemicals such as Benzene

The nature of gene mutation on the encoded polypeptide for substitution mutation

change the sequence of amino acids in the primary structure

therefore alter bonds formed in tertiary structure e.g ionic/disulphide

this would affect the final shape of the tertiary structure of the protein

could be silent if the genetic code is degenerate

The nature of gene mutation on the encoded polypeptide for a deletion or addition mutation

causes a frameshift

This is when the reading frame for the triplet code changes and it can therefore alter all the amino acids after the mutation

The nature of gene mutation on the encoded polypeptide for inversion mutation

take a sequence of amino acids in the polypeptide chain and have them in reverse order

The nature of gene mutation on the encoded polypeptide for a translocation mutation

widespread effects on a number of polypeptides leading to abnormal phenotypes

The nature of gene mutation on the encoded polypeptide for a duplication mutation

often causes the repeat of an amino acid numerous times in a polypeptide chain if the duplication is of a codon