Mutations

Mutations are changes in the DNA that can result in no protein or an altered protein being synthesised.

Single gene mutations involve the alteration of a DNA nucleotide sequence as a result of the substitution, insertion or deletion of nucleotides.

Nucleotide insertions or deletions result in frame-shift mutations.

Frame-shift mutations cause all of the codons and all of the amino acids after the mutation to be changed. This has a major effect on the structure of the protein produced.

Nucleotide substitutions — missense, nonsense and splice-site mutations.

Missense mutations result in one amino acid being changed for another. This may result in a non-functional protein or have little effect on the protein.

Nonsense mutations result in a premature stop codon being produced which results in a shorter protein.

Splice-site mutations result in some introns being retained and/or some exons not being included in the mature transcript.

Duplication is where a section of a chromosome is added from its homologous partner.

Deletion is where a section of a chromosome is removed.

Inversion is where a section of chromosome is reversed.

Translocation is where a section of a chromosome is added to a chromosome, not its homologous partner.

The substantial changes in chromosome mutations often make them lethal.