How do point mutations happen
- most common base pairing occurs btween A:T and G:C
- rare base pairing CAN occur between A:C and G:T due to tautomeric shifts
Tautomer
a transient (non-permanent) isomeric form of a nitrogenous base
Point mutation in sickle cell anemia
- an inherited disorder of RBCs involving the HBB gene
- encodes for B-globin protein
- hemoglobin: a tetramer formed of 2 alpha/beta global subunits
- HBB gene undergoes mutation - glutamic acid to valine at position 6
frameshift mutation
insertion or deletion of one or several bases that may change all or part of the open reading frame (indels)
- changes polypeptide seq of protein
Indels
change the open reading frame & DNA seq
Small indels
- replication slippage results in addition/omission of a nucleotide
- DNA regions w many copies of repeated seq are most susceptible
Large indels
- several hundred to thousands of nucleotides
Trinucleotide repeats
3 nucleotides that’re repeated several times in succession
- not a mutation (but prone & considered a hotspot)
- repeated a few to 50 times
Expanded trinucleotide repeats
A type of insertion that arises due to replication slippage in regions of the genome w TR
Huntingtons Disease
Progressive neurodegenerative disorder characterized by:
- involuntary movements, declines in cog func, altered mood
- caused by expanded CAG trinucleotide repeat on chromosome 4
- pathological # of CAG repeats (>35)
Anticipation
- a genetic phenomenon in which a disorder worsens with each generation
- arises due to replication error during the production of gametes
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Module 413
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Module 5 - Part 112
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Module 5 - Part 219
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Module 6 - Part 17
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Module 6 - Part 214
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Module 1 - Part 118
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Module 1 - Part 211
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Module 2 - Part 113
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Module 2 - Part 210
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Module 3 - Part 16
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Module 3 - Part 215
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Module 7 - Part 118
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Module 7 - Part 26
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Module 8 - Part 112
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Module 8 - Part 219
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Module 9 - Part 117
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Module 9 - Part 244
