1. Mutations

2. 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
Defined: one nucleotide is substituted for another
May be repaired by DNA polymerase
May lead to amino acid change
See animation
May not lead to any change
Ex: DNA “CCC” is mutated into “CCG”
Same amino acid is created (glycine)

3. Gene: Frame Shift MutationC 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
Defined: insertion/deletion of a nucleotide
Entire sequence of DNA/RNA after the mutation is shifted (see animation)
Much more serious to the structure/function of the final protein
mRNA sequence may have early or late “stop codons”

4. Gene: Frame Shift MutationC 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

5. Chromosome Mutations
Translocation: Chromosome segments combine with nonhomologous chromosome
Many genes wind up on entirely different chromosomes
Gene cut apart
½ on chr #5, ½ on chr #8

6. Down’s
Syndrome

7. Impact on Offspring Somatic cell mutations Affect only the individual
Not passed on to future generations
Ex: Muscle cell mutation
Germ cell mutations
May be passed to future generations
Ex: Sperm cell mutation

8. Mutation Causes Mutagen: agents in the environment that can change DNA
Speed up replication process
Break apart nucleotides
Ex: UV sunlight breaks hydrogen bond between thymine (T) and adenine (A)