3. 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

4. Gene: Point Mutations 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) DNA mRNA Amino acids

5. 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

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

7. Gene: Frame Shift Mutation DNA mRNA Amino acids

8. 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…

9. 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)

10. Review 1)How are proteins affected if the DNA code is mutated? Example: ATTCGAGG is mutated to ATTCGTGG 2)What is the difference between a point mutation and frame shift mutations? 3)When are mutations passed on to future generations? 4)What are germs cells? 5)What is a mutagen and how do they cause problems? 6)Are all mutations considered bad/dangerous? Explain.