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Topic 8
Mutations
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Fatima M
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Gene mutation
Alteration of a
base sequence
in DNA
Gene mutations
are likely to occur when DNA is
replicating
, which happens in interphase of the cell cycle
Mutation
impact
Changes the
amino
acid
sequence
(primary structure) in the polypeptide chain,
altering
the
3D
shape
and function of the protein
Mutagenic
agents
High
energy ionizing radiation (alpha, beta, X-rays, gamma rays)
Carcinogens
(chemicals like tobacco smoke, mustard gas, peroxides)
Exposure to
mutagenic
agents increases the risk of spontaneous mutations, but does not
guarantee
a mutation will occur
Types of gene mutations
Addition
(frame shift)
Deletion
(frame shift)
Substitution
(sometimes silent)
Inversion
Translocation
Addition
mutation
One DNA
nucleotide
is accidentally added, causing a frame shift in the subsequent
triplets
Deletion
mutation
One DNA
nucleotide
is
deleted
, causing a frame shift (to the left) in the subsequent triplets
Substitution mutation
One DNA nucleotide is swapped for another, sometimes resulting in a different amino acid but sometimes a
silent
mutation
Inversion
mutation
A section of DNA detaches and
rejoins
in the
reverse
orientation
Translocation
mutation
A section of
DNA
breaks off one
chromosome
and attaches to a different chromosome