GENETIC MUTATIONS
Errors in Protein Synthesis
Mutation
click for a short video.
◦A mutation is a change in the DNA sequence.
◦If the change is in the areas of DNA that are
between the genes, not usually a problem.
◦If the change is in the parts of DNA that code for
proteins (genes); may be a problem.
◦ Point mutation – there is a swap of
one of the DNA nucleotides.
AAA TTT à AAA TAT
◦ These changes can result in a small
change in a protein (missense), a
stoppage of a protein (nonsense) or
no change (silent mutation).
◦ Two men sat and had tea.
◦ Two men Sat and had tea
◦ Two men sat and had sea
◦ Two me.
Types of
Mutations
Small changes
in the DNA
Go to
http://learn.genetics.utah.edu/content/basics/outcomes/
to learn more!
Examples
◦ Extra Toed Cats
◦ A single base
change causes the
“on/off switch” to
trigger incorrectly,
causing extra toes
to grow.
Example 2: Double Muscled Cattle
◦A simple deletion causes a
misshapen “stop” codon.
The muscles do not stop
growing.
◦ Addition or deletion – there is a change
in the number of nucleotides.
AAA TTT à AAA ATT T or
à AAT TT
◦Use your Codon Chart to check this
mutation:
◦ AAA TTT CCC GGG à
◦ AAT TTC CCG GGA
◦What is the sequence of amino acids
for each chain?
Frameshift
Major
change in
DNA
codons!
Back to two men….
◦ Two men sat and had tea.
◦ Two men Sat and had tea
◦ Two men sat and had sea
◦ Two me.
◦ Twm ens ata ndh ads ea
◦ Two ome nsa tan dha dte a
normal
silent
missense
nonsense
deletion frameshift
addition framshift
Frameshift Mutation
All the codons beyond the
mutation are changed!
Frameshift
Huge
changes in
the DNA.
In Review
Which type of
mutation is the
most
catastrophic
to the
organism?
The least?
TaySachs
Disease
Both of
these
children
have died.
v Normal until 6 months
v Nerves deteriorate
v Child becomes deaf, blind, unable to
swallow
v Death usually by age 4.
Tay-Sachs is
a frameshift
mutation.
ENZYMES
Important Enzymes
Enzyme
Function
◦Replicase
◦ Makes mRNA
◦DNA Helicase
◦ Unwinds DNA helix
◦DNA Polymerase
◦DNA Ligase
◦DNA Nuclease
◦ Adds nucleotides to leading DNA strand (5’
to 3’), proofreads
◦ Glues segments on lagging strand
◦ Edits new DNA