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Mutations
are changes in the genetic material of a cell
or virus
Point Mutations
are chemical changes in just one or a few nucleotide
pairs of a gene
Insertions and deletions
are additions or losses of nucleotide pairs in a gene
frameshift mutation
insertion or deletion of nucleotides may alter the reading
frame of the genetic message, producing a
A mutation may alter the sequence within a____and affect the rate of transcription (+/-)
promoter
Mutations may occur in other_____or
operator sites
regulatory elements
Germ-line cells
give rise to
gametes
Somatic cells
are all other body
cells
§ Can occur early or late in
development
§ Gives a genetic mosaic with
patches of mutant tissue
Spontaneous mutations
§ From abnormalities in biological processes, free
radicals/reactive oxygen
§ Rates vary species to species and gene to gene
§ Background mutation rate approximately 1 mutation / million
genes (1 in 106)
Induced mutations
§ Caused by environmental agents
§ Higher rate than spontaneous mutations
Mutagens
chemical or physical agents that alter DNA
Ionizing radiation
has high energy and penetrates deeply to create free radicals
§ X rays and gamma rays
§ Cause deletions or breaks in one or both DNA strands
Nonionizing radiation
has less energy and can only penetrate the surface
§ UV light
Mismatch repair
occurs when
mismatched bases are corrected
after DNA synthesis is complete
proofreading process
reduces the error rate to
about one mistake in 10
million base pairs
