1. MUTATIONS

2. Mutations Defined: A change in an organism’s DNA.
Many kinds of mutations can occur, especially during replication.
2 Types:
1) Gene Mutations:
A point mutation, substitutes one nucleotide for another.
mutated
base

3. Gene: Point Mutations A C A G T G T G T C A A A U G U C A A C C A G U
DNA U G U C A A C C A G U U U
mRNA
Amino acids
cysteine
histidine
glutamine
glutamine
phenylalanine
May lead to amino acid change
See animation
May not lead to any change (Silent Mutation)
Ex: DNA “CCC” is mutated into “CCG”
Same amino acid is created (glycine)

4. Gene Mutations Continued…
A frameshift mutation (another type of gene mutation) inserts or deletes a nucleotide in the DNA sequence.
Entire sequence of DNA/RNA after the mutation is shifted (see animations)
Much more serious to the structure/function of the final protein
mRNA sequence may have early or late “stop codons”

5. Gene: Frame Shift Mutation (deletion)C A G T G G T C A A A C
DNA U G U C A C C A G U U U G
mRNA
Amino acids
cysteine
histidine
histidine
glutamine
serine
phenylalanine
leucine
Gene: Frame Shift Mutation (insertion) A C A G T C G G T C A A A
DNA U G U C A G C C A G U U U
mRNA
cysteine
histidine
glutamine
phenylalanine
Amino acids
glutamine
proline
valine

6. What type of mutation would this be?
Original: The fat cat ate the wee rat.
Mutation: The fat hat ate the wee rat.
Point Mutation

7. Which has a much large effect on the end result?
What about this one?
Original: The fat cat ate the wee rat.
Mutation: The fat caa tet hew eer at.
Frameshift deletion
Which has a much large effect on the end result?
Point or frameshift mutation?
Frameshift Mutation

8. 2) Chromosomal Mutations
Affect many genes.
Chromosomal mutations may occur during crossing over
Gene duplication results from unequal crossing over.

9. Translocation results from the exchange of DNA segments between nonhomologous chromosomes.

10. Mutations May or May Not Affect Phenotype
Some gene mutations change phenotype.
Some gene mutations do not affect phenotype.
May cause a premature stop codon.
May be silent.
May occur in a noncoding region.
Can change protein structure.
May not affect protein structure.
May cause gene regulation.
blockage
no blockage
Ex: Cysitc Fibrosis (mutation causes excess mucus build up in airways)

11. Impact on Offspring Somatic cell mutations Germ cell mutations
Affect only the individual
May be passed to future generations (either harmful or beneficial)
Not passed on to future generations
Ex: Sperm cell mutation
Ex: Muscle cell mutation
In nature, these are often removed from a population (natural selection)- as these don’t usually survive.

12. Causes of Mutations Replication errors can cause mutations.
Mutagens, such as UV ray and chemicals, can cause mutations.
Some cancer drugs use mutagenic properties to kill cancer cells.