1. Mutations

2. Mutations Defined: any change in an organism’s DNA
Where: Single genes or entire chromosomes
Some gene mutations change phenotype (physical characteristics)
Example: Can cause a premature stop codon
Some gene mutations don’t change phenotype.
Example: Could be silent or occur in a non-coding region
When: Throughout the life of the cell

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
Defined: one nucleotide is substituted for another
Often repaired by spellchecker enzyme
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. Point Mutation and Sickle Cell Disease
Hemoglobin (protein) is made from 574 amino acids
Sickle cell disease is caused because of 1 wrong amino acid

5. Gene: Frame Shift MutationC A G T T G T C A A A C
DNA U G U C A A C A G U U U G
mRNA
Amino acids
cysteine
glutamine
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 an early or late “stop codon”

6. 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

7. Impact on Offspring Somatic cell mutations Affect only the individual
Not passed on to future generations
Ex: Muscle cell mutation
Germ cell mutations
Germ cells = the diploid cells that undergo meiosis to make sperm & egg
May be passed to future generations
If the mutated sperm above were to fertilize this egg…

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

9. Example: ATTCGAGG is mutated to ATTCGTGG
Review
How are proteins affected if the DNA code is mutated?
Example: ATTCGAGG is mutated to ATTCGTGG
What is the difference between a point mutation and frame shift mutations?
When are mutations passed on to future generations?
What are germs cells?
What is a mutagen and how do they cause problems?
Are all mutations considered bad/dangerous? Explain.