Introduction
DNA ass genetic material is relatively stable.  However, under many physiological conditions it may also undergo some changes.  A mutation is a permanent change in the DNA sequence of a gene. Mutations in a gene's DNA sequence can alter the amino acid sequence and therefore affect the function of the gene product.   Mutation can occur at either DNA or chromosome level, spontaneously or induced.

DNA mutation types
DNA mutation includes several types according to its consequence: base pair substitution (transversion or transition); missense mutation, nonsense mutation, neutral mutation, silent mutation and frame-shift mutation. 

Cause of mutation
Mutation can be spontaneous, due to the replication errors and/or chemical reactions in cells (such as depurination and deamination).  DNA mutation can also be induced by radiation and chemical mutagens. 

DNA repair mechanisms
Overall there are two classed of DNA repair mechanisms: direct repair of lesion and repair involving excision of base pairs (BER).  Direct repair includes DNA polymerase proofreading, light repair of thymidine dimers, and repair of alkylatiion damage.  BER includes excision repair, glycosylase repair, mismatch repair and SOS response. 

DNA mutation includes base pair substitution (transversion or transition); missense mutation (altered amino acid), nonsense mutation (truncated protein), neutral mutation (no phenotypical effect, similar amino acid replacement), silent mutation (with nucleotide change but amino acid remains the same) and frame-shift mutation (change all amino acid sequence after the mutation site).  DNA mutation can be spontaneous to the replication errors and/or chemical reactions in cells (such as depurination and deamination).  It can also be induced by radiation and chemical mutagens.  Mutated DNA can be repaired by various cellular mechanisms including direct repair of the lesion and repair involving excision of base pair. 

• Internal concept map to explain mutation and DNA repair.
• Pictorial explanation of each class of mutations.
• Key concept sheet and thought-provoking question sheets.
• Chemical structure explain causes of mutations on DNA
• Step by step diagrams and charts to show DNA repair procedure
• Table giving DNA repair defect-caused genetic diseases

Mutation

• Definition
• Levels of mutation
• Spontaneous vs. induced
• Base pair substitution
• Missense mutation
• Nonsense mutation
• Neutral mutation
• Silent mutation
• Frame-shift mutation

Causes of mutations

• Mutation rate and frequency
• Replication erros
• Depurination
• Deamination
• Radiation-induced mutation
• Chemical-induced mutation

DNA repair

• DNA polymerase proofreading
• Light repair
• Repair of akylating damage
• Excision repair
• Repair by glycosylase
• Mismatch repair
• SOS response
• DNA repair defects and diseases