1. Mutations: Changing DNA SBI4U Biology

2. Mutation: A change in the DNA sequence that is inherited as the DNA is transmitted through cell division.  Changes in number or structure of chromosomes  Spontaneous  Induced  Mutagens = UV, X Rays, other radiation; chemicals; heavy metals

3. Categorising mutations 1. By effect on structure 2. By consequences on resulting proteins

4. 1. Mutations by effect on structure a) Point mutations Mutations that occur to a specific base pair in the genome. b) Chromosomal mutations Mutations that involve large segments of DNA.

5. Point mutations Substitution: One base pair is replaced with another

6. Point mutations (cont`d) Deletion: One or more base pairs is eliminated from the DNA sequence

7. Point mutations (cont`d) Insertion: One or more base pairs is inserted into the DNA sequence

8. Frameshift mutations Deletions and insertions of 1-2 base pairs will result in a shift in the reading frame. “frameshift mutations”

9. Deleting or inserting 3 base pairs is not considered a frameshift mutation... why??

10. Chromosomal mutations Large scale changes to chromosomes Inversion : The reversal of a segment of DNA within a chromosome. Results from breaking and rejoining (upside down)

11. Chromosomal mutations (cont`d) Translocation: A fragment of DNA moves from one part of the genome to another. Can result in a “fusion protein”

12. Chromosomal mutations (cont`d) Gene duplication: Duplication of a coding region of DNA along a chromosome Results from crossing over of misaligned homologues during meiosis I

13. Chromosomal mutations (cont`d) Deletion: Part of a chromosome is deleted and becomes “missing”

14. Chromosomal mutations (cont`d) Insertion: The complement of deletion. Part of another chromosome is inserted.

15. Gross Chromosomal

17.  Aneuploidy = incorrect number of chromosomes  Trisomy = extra chromosome (2n +1)  Monosomy = missing chromosome (2n -1)  Triploid = 3n, Tetraploid = 4n

18. Trisomy & Monosomy

19. 2. Mutations by consequence on resulting protein a) Silent mutations b) Missense mutations c) Nonsense mutations

20. Silent mutations Does not result in a change in amino acid sequence  no phenotypic change; no effect on the cell How? May occur within an intron Redundancy of genetic code ACA and ACU are both codons for threonine

21. Missense mutations Results in a change to a codon  The wrong amino acid is incorporated  Does not necessarily drastically alter protein function Checkpoint: Can you classify this mutation by its effect on structure?

22. Nonsense mutations A codon is converted to a stop codon  truncated protein is produced Checkpoint: Can you classify this mutation by its effect on structure?

23. Mutation Examples: I LOVE HER SO MUCH I COULD MARRY HER. Silent: I LOVE HER SO MUCH I COULD WED HER. Missense: I LOVE HER SO MUCH I COULD PUNCH HER.

24. Mutation Examples: I LOVE HER SO MUCH I COULD MARRY HER. Chain Termination: I LOVE HER SO MUCH I COULD. Nonsense: I LOVE HER SO MUCH I COULD MARY HERE THIRST PINK UTAH MONGOOSE LABEL WINE FLIRT LAVA LAMP TOOL BARGE MAPLE NOSE HAIR RITZ CRACKER CONSPIRACY GONG SHOPPING SPREE WIT ’ S END NEVADA WONDERFUL SQUID RICE KANGAROO CELEBRATE WART…

25. Mutation Examples: I LOVE HER SO MUCH I COULD MARRY HER. Deletion Frameshift: I LOVH ERS OM UCHI C OULDM ARRYH ER Insertion Framshift: I LOXV EHE RS OMUC H ICOUL DMARR YHE R

26. Consolidation MUTATIONS Effect on structure Point mutations substitutiondeletioninsertion Chromosomal mutations inversiontranslocationduplicationdeletioninsertion Effect on protein SilentMissenseNonsense

27. Causes of mutations Innate Spontaneous: Due to errors in replication Environmental Exposure to mutagenic agents UV radiation, X rays, chemicals