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mutations-recombination
raw material for evolution
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Types of mutations
- -only focusing on gene mutations
- 1. mutations affecting single base-pairs
- 2." " alter the # if copies of small repeated sequences.
- ex Fragile x
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Point mutations
- 1. Base substitutions
- Transition
- -purine ---> purine A to G
- -Pyrimidine ----> purine C to T
- Transversion
- -purine ----->pyrimidine C to A or G
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Point mutations -"Indels"
Insertions or deletions
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Functional Consequences (@ protein)
1. Frameshift
- 1. Frameshift (when insertion or deletion)
- AAG ACT CCT wild type
- ^insert G
- AAG AGC CTC T..
- Better of it happens later on in the sequence.
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Functional Consequences (@ protein)
2. silent
- (synonymous) = same AA
- AGG -----> CGG
- Arg Arg
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Functional Consequences (@ protein)
3. missense
- (non-synonymous) = diff AA
- AAA -----> AGA - variable affect on protein Lys Arg
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Functional Consequences (@ protein)
4. nonsense
- = stop codon
- CAG -----> UAGGlutamine(?) Amber stop
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causes
- spontaneous (internal)
- induced (external)
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spontaneous (internal)
- 1. DNA Polymerase can insert wrong base
- -often due to tautomers*
- 2. metabolic by-products:
- example - reactive oxygen
- H2O2, O*2 -superoxide, *OH
- - can result in mispairing, transitions/tranversion
- @ replications
- 3. Depurination
- - covalent bond between the sugar and base (purine A,G) is slightly unstable. -->
- H2O can react and cause the base to detatch.
- A C G T G leaves
- T G C A
- 4. Deamination: remove amine
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Tautomers
- -base analogs
- - They are isomers, that differ in the positions of atoms/bonds
- -The problem is these can pair in abnormal conbinations
- T-G A-C
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Induced
1. Chemicals mutagens
- Similar to spontaneous, just external cause
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Induced
2. Physical mutagens
- X-rays, gamma: tend to nick (can be ss break or ds break (translocation) the backbone),
- 2. Delete bases
- 3. Oxidizing base
UV = causes alterations in DNA called "photoproducts"
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