Mutations

• Chromosome


  Structure containing the genetic material encoded in DNA
• Deletion (of chromosome)


  A chromosome mutation in which a section of a chromosome is removed
• Deletion (of nucleotides)


  Single-gene mutation involving removal of a nucleotide from a sequence
• Duplication


  A chromosome mutation in which a section of a chromosome is added from its homologous partner
• Frameshift mutation


  Gene mutation in which all codons and amino acids after the mutation are altered
• Insertion


  Single-gene mutation in which an additional nucleotide is added to a sequence
• Inversion


  A chromosome mutation in which a section of chromosome is reversed
• Missense mutation


  A nucleotide substitution mutation which results in one amino acid being changed for another
• Nonsense mutation


  A nucleotide substitution mutation which results in a premature stop codon being produced
• Splice-site mutation


  A nucleotide substitution mutation which results in some introns being retained and/or some exons being removed
• Substitution


  Single-gene mutation in which one nucleotide is replaced by another
• Translocation


  A chromosome mutation in which a section of a chromosome is added to another which is not its homologous partner
• Mutation


  A change in the DNA that can result in no protein or an altered protein being synthesised
• Mutations are spontaneous
• Mutations


  • Can involve changes in the structure of a gene
  • Can involve changes in the structure of a chromosome
  • Can involve changes in the number of chromosomes
• Mutations result in no protein or an alternative protein being expressed
• Genetic disorders are caused by changes to genes or chromosomes that result in the proteins not being expressed or the proteins being expressed but not functioning properly
• Single gene mutations


  Involve the alteration of a DNA nucleotide sequence, such as substitution, deletion, or insertion of nucleotides
• For a protein to work properly it must have the correct sequence of amino acids
• If the order of bases in the DNA is changed, this can affect the structure and function of the protein which is manufactured
• Nucleotide substitution (point mutation)

  1. DNA nucleotide is replaced with another

  2. Can result in altered amino acids, a premature stop codon, or changes to mRNA splicing
• Nucleotide substitution mutation


  Unlikely to greatly affect protein structure and function if the substitution results in a different but still functional amino acid
• Nucleotide deletion


  1. A nucleotide is deleted from the DNA sequence

  2. Causes a frameshift mutation, altering all amino acids after the deletion
• Nucleotide deletion mutation


  Can have lethal effects on the organism depending on the role of the affected protein
• Nucleotide insertion


  1. A nucleotide is inserted into the DNA sequence

  2. Causes a frameshift mutation, altering all amino acids after the insertion
• Nucleotide insertion mutation


  Can have lethal effects on the organism depending on the role of the affected protein
• Single gene mutations


  Alteration of a DNA nucleotide sequence as a result of the substitution, insertion or deletion of nucleotides
• Types of nucleotide substitutions

  • Missense
  • Nonsense
  • Splice-site
• Nucleotide insertions or deletions


  Result in frame-shift mutations
• Chromosome structure mutations


  Alterations to the structure of a chromosome
• Types of chromosome structure mutations

  • Duplication
  • Deletion
  • Inversion
  • Translocation
• The substantial changes in the structure of chromosomes caused by these mutations means that they are often lethal