8.7 Mutations
KEY CONCEPT
Mutations are changes in DNA that may or may not
affect observable traits/characteristics.
8.7 Mutations
Some mutations affect a single gene, while others affect
an entire chromosome.
• A mutation is a change in an organism’s DNA.
• Many kinds of mutations can occur, especially during
replication.
• A point mutation substitutes one nucleotide for another.
mutated
base
8.7 Mutations
• Many kinds of mutations can occur, especially during
replication.
– A frameshift mutation inserts or deletes a nucleotide in
the DNA sequence.
8.7 Mutations
Mutations may or may not affect observable traits.
– A mutation may cause a premature stop codon.
– A mutation may change protein shape or the active site.
The coronary artery supplies blood to the heart. A
mutation exists that protects against blockages.
blockage
no blockage
Cystic Fibrosis is
caused by a deletion.
8.7 Mutations
• Some gene mutations do not affect observable traits.
– A mutation may be silent.
– Many amino acids have more than one code
– Ex: AAG and AAA are both lysine
– A mutation may occur in a noncoding region.
– A mutation may not affect protein folding or the active
site.
– Changed amino acid may have the same size and
polarity and may not change the function much
8.7 Mutations
Impact on Offspring
• Mutations in body cells do not affect offspring. These
cells are not passed on to offspring.
• Mutations in sex cells are passed on and can be harmful or
beneficial to offspring.
• Usually, offspring do not develop properly and are not
able to reproduce
• Natural selection often removes mutant genes from a
population when they are less adaptive.
• Rarely, a mutation results in a superior trait that is
passed on and causes an increase in population.
8.7 Mutations
Mutations can be caused by several factors.
**Mutations can happen faster than
the body is able to repair them
• Replication errors can cause
mutations (DNA Polymerase
does not detect them all).
• Mutagens, such as UV ray and
chemicals, can cause mutations.
– UV light breaks the T-A bond and
causes the them to bond incorrectly.
This can result in cancer.
• Some cancer drugs use
mutagenic properties to kill
cancer cells.
8.7 Mutations
Review
• Where/when do most mutations occur?
• What is the difference between a point mutation (1 type)
and a frameshift mutation (2 types)?
• Contrast the results of a point mutation and a frameshift
mutation
• Why aren’t mutations in body cells passed on to the next
generation?
• What’s the big deal? Doesn’t the DNA have
proofreading/repair mechanisms?
• THINK: How could a mutated gene produce a shorter
protein than the normal gene?