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Mutation
Mutation
• Mutation is a change in the
genetic code
• Most mutations are harmless
• Some are harmful
• Few are helpful
• Mutations fall into 2 categories
each of which have multiple
variations
1. Gene mutations (aka point
mutations)
2. Chromosome mutations
Gene/Point Mutations
• Mutations at a single
nucleotide (base pair –
bp) in a gene
1. Substitution – one bp
changes letters
1.Silent – no change to
protein
2.Missense – change a
single amino acid
(AA) into a different
AA
3.Nonsense - change
an AA into a stop
codon
Substitution
Gene/Point Mutations
2. Frameshift Mutations – change
the reading frame (size: # of
bp’s) of the gene
• Insertion – add 1 bp to the gene
• Deletion – remove 1 bp from the
gene
Deletion
Insertion
Chromosome Mutations
• Massive
mutation of
part or all of a
chromosome
• Many genes
can be
affected
1.
2.
3.
4.
Deletion
Duplication
Inversion
Translocation
Deletion
Duplication
Inversion
Translocation
Mutagenesis
• The creation of a mutation
A. Spontaneous mutations: errors
during DNA replication
B. Mutagen: physical (radiation) or
chemical (carcinogen) agent
that triggers mutation