1. DNA Mutations

2. Victims of Chernobyl - Mutations

3. What are mutations? Mutations are a change in the genetic material of a cell (i.e. the genes).

4. Key Terms Mutation (Germ cell and Somatic) ◦ Gene mutation ◦ Chromosome mutation Point Mutation ◦ Substitution Frameshift mutation ◦ Insertion ◦ Deletion

5. What can cause mutations? These mutations can come from the environment (such as radiation = cancer) or they can come from errors in transcription and translation

6. 2 Types of mutations Germ cell mutation: These are mutations that occur in the sperm cell or egg cell. ◦ These mutations will be passed down from parent to child Somatic mutations: Occur in all other cells in the body ◦ E.g. cancer

7. Where can mutations occur? Gene mutations involve large segments of DNA or a single nitrogenous base. Chromosome mutations occurs when an entire chromosome is lost or the structure of it changes ◦ We will look at chromosome mutations later

8. 2 Types of Gene Mutations Point mutation - Substitution Frameshift mutation - Insertion - Deletions

9. Point Mutation - Substitution Substitution occurs when a single nitrogenous base is replaced with a different nitrogenous base E.g.

10. Frameshift Mutations – Insertion/ Deletion Insertion occurs when one or more nitrogenous base is added Deletion: Occurs when one or more nitrogenous base is deleted

11. 5 Possible Results of a Mutation 1. Silent Mutation 2. Substitution 3. Premature Stop 4. Codon Deletion or Insertion 5. Frame Shift

12. 1. Silent Mutation (Point Mutation) Occurs when a nitrogenous base is substituted but the change still produces the same amino acid. E.g. AGA and AGG both produce the amino acid Arginine

13. 1. Silent Mutation

14. 2. Substitution (Point Mutation) When an amino acid is substituted and the new codon makes a different amino acid E.g. AGA makes Arginine and GGA makes Glycine

15. 2. Amino Acid Substitution

16. 3. Premature Stop (Point Mutation) When a substitution results in the formation of a STOP codon. This causes the amino acids after the STOP codon from being produced. E.g. Original RNA AUGAAACAAGUUGCU Mutated RNA AUGAAAUAAGUUGCU

17. 4. Codon Deletion or Insertion A whole new amino acid is added, or one is missing from the mutant DNA E.g. Original RNA AUGAAACAA Mutated RNA AUGGUUAAACAA

18. 5. Frame Shift When a deletion or insertion results in a the shifting of codons causing a large change in the amino acids being produced E.g. Original RNA AUGAAACAAGUC Mutated RNA AUGAUAACAAGUC

19. 5. Frame Shift

20. The Impact of DNA mutations Silent mutations will not effect us because these mutations still produce the same amino acid A substituted mutation that makes a s single different amino acid will have a small effect ◦ This is because only one amino acid is changed

21. The Impact of DNA mutations A premature STOP mutation will have a large impact because it will stop making the protein A deletion mutation that removes an amino acid will often lead to a small impact. ◦ This is because only one amino acid is affected

22. The Impact of DNA mutations A frameshift mutation can have a severe impact because it can produce an entirely different protein

23. Examples Sickle Cell Anemia (Substitution) Colour Blindness (Substitution)

24. Examples Thalassemia (Premature STOP codon)

25. Williams Syndrome (Deletion)

26. Tay-Sachs Disease (Frameshift) Symptoms in infants include: Slowing down of development Weakening of muscles Loss of motor skills such as turning over, sitting, and crawling. As the disease progresses, other symptoms may also occur, including: Seizures Increased startle reflex to noise Vision loss Hearing loss Inability to swallow Mental retardation Paralysis Dementia