3. Defined: a change in an organism’s DNA Where: DNA or Chromosomes When: During replication, Synapses, or Crossing-Over Mutations can affect a single gene or an entire chromosome: –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

4. Gene: Point Mutations Defined: one nucleotide is substituted for another Often repaired by DNA Polymerase (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) DNA mRNA Amino acids

5. Gene: Frame Shift Mutation (deletion) 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” DNA mRNA Amino acids

6. Gene: Frame Shift Mutation (insertion) DNA mRNA Amino acids 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”

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 (either harmful or beneficial) – Ex: Sperm cell mutation Natural selection often removes mutant alleles from a population when they are less adaptive.

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)

9. REview 1)What is a mutagen and how do they cause problems? 2)How are proteins affected if the DNA code is mutated? Example: ATTCGAGG is mutated to ATTCGTGG 3)What is the difference between a point mutation and frame shift mutations? 4)When are mutations passed on to future generations? 5)Are all mutations considered bad/dangerous? Explain.