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  • Created by: Steff06
  • Created on: 24-04-16 17:07

Examples and classes of mutations

Mutation = RANDOM CHANGE to genetic material.

Chromosome mutation = Change to number or STRUCTURE of chromosomes. 

Substances causing mutations:

  • Tar,
  • Gamma rays,
  • UV light,
  • X-rays.

Classes of mutations:

POINT mutation/SUBSTITUTION - One base pair replaces another.

INSERTION/DELETION - Causes frameshift.

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Effects of substitutions, insertions and deletions

3 types of point mutations: 

  • Nonsense,
  • Misense,
  • Silent.

Nonsense and misense: Causes different amino acid to be produced. 

Therefore chain is affected. Nonsense codes for STOP.

Silent: Same amino acid is produced.

Therefore chain is unaffected. 

Insertion/deletion: Causes frameshift.

All affected from mutation onwards.

Causes different 3D structure.

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Beneficial, neutral and harmful mutations

If the insertion/deletion was closer to the start of the chain, it would have a larger effect as it would cause more amino acids to be changed. 

Neutral mutations:

  • Neither beneficial or harmful effect. 
  • Produces no change if mutation is in non-coding region of DNA. 
  • It is a silent mutation. 
  • E.g. ability to roll tongue,free/attached ears. 

Harmful mutations:

  • Paler skin = Burned, skin cancer.
  • Sunlight not intense enough to produce sufficient vitamin D in darker skinned.

Beneficial mutations:

  • Melanin in darker skinned protects from harmful UV light.
  • Paler skin = Produces more vitamin D. 
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