Section 13.3
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The sequence of bases in DNA are like the
letters of a coded message.
What would happen if one or a few of those
letters changed accidentally, altering the
message?
What effects would you predict such changes
would have on genes and the polypeptides
for which they code?
A permanent change of the
nucleotide sequence of the
DNAof an organism.
- Chromosomal mutations
- Point mutations
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A mutation involving a long
segment of DNA.
These mutations can involve
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deletions
insertions
Inversions
translocations
In some cases, the deleted
sections may attach to
another chromosome,
disrupting both the one that
loses the DNA and the one
that gains it.
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A mutation involving a single nucleotide base
◦ substitution
◦ insertion
◦ Deletion
Substitutions
– can affect one amino acid.
- may have no affect
…….It all depends on what is substituted
Examples:
CCC
 CCA
proline  proline
CCC

ACC
proline  threonine
Insertions / Deletions
 These are referred to as frameshift mutations
because everything downstream of the
mutation in affected.
a. Insertions
b. Deletions
THE CAT ATE THE DOG
THE CAT TAT ETH EDO G
THE CAA TET HED OG
(Insertion of extra T)
(Deletion of T)
Mutations may be artificially or naturally
induced by Mutagens, including
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Pesticides
Tobacco smoke
Environmental pollutants
Radiation
Outcome may be
◦ Good
◦ Bad
◦ Neutral
Click Smog for video