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Mutations: Changing DNA

Mutations: Changing DNA. SBI4U Biology. 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.

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Mutations: Changing DNA

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  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 • By effect on structure • By consequences on resulting proteins

  4. 1. Mutations by effect on structure • Point mutations • Mutations that occur to a specific base pair in the genome. • 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

  16. 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 • Silent mutations • Missense mutations • 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 WEDHER. 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

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

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