mutations

• a mutation is a random spontaneous change in an organisms genome.
• There are 2 types of mutations:

  • gene mutations: change in the DNA structure a gene
  • chromosome mutations: change in the structure or number of chromosomes
• Single gene mutations involve the alteration of a DNA nucleotide sequence as a result of:

  • the substitution of nucleotides. (replacing 1 nucleotide with another).
  • insertion of nucleotides.
  • deletion of nucleotides.
• 1. Missense mutations – result in one amino acid being changed for another. This may result in a non-functional protein or may have little effect on the protein depending on the amino acid that has been changed.Example Sickle cell disease.
• 1. Nonsense mutations result in premature stop codon being produced which results in a shorter protein.Example Duchenne Muscular dystrophy.
• 1. Splice site mutations result in some introns being retained and/or some exons not being included in the mature transcript.Example beta thalassemia.
• The effect of an insertion or deletion of a nucleotide results in frame shift mutations. ,
• • Cystic fibrosis – Deletion
  • Tay-Sachs disease - Insertion
• Frame shift mutations cause all of the codons and all of the amino acids after the mutation to be changed.

  This has a major effect on the structure of the protein produced.
• CHROMOSOME MUTATION 1:

  Duplication – a section of a chromosome is added from its homologous partner.
• CHROMOSOME MUTATION 2:

  Deletion is where a section of the chromosome is removed.
• CHROMOSOME MUTATION 3:

  Inversion is where a section chromosome is reversed.
• CHROMOSOME MUTATION 4:

  Translocation is where a section of a chromosome is added to a chromosome,

  that is not its homologous partner.
• The substantial changes in chromosome mutations often make them lethal.
• Changing one amino acid could cause a protein to function less effectively because the structure of the protein is altered, or the protein does not fold properly.