DNA and the structure of proteins

• What is a mutation

  ~An alteration to the DNA base sequence

  ~Often arise spontaneously during DNA replication
• What are addition and deletion mutations


  Where one or more nucleotides are either inserted or deleted from the DNA sequence
• What is a substitution mutation


  Where one nucleotide in the DNA sequence is replaced by another
• What is a duplication mutation


  Where one or more nucleotides duplicate and repeat
• What is an inversion mutation


  Where a group of nucleotides become separated from the DNA sequence, then rejoin in the reverse order
• What is a translocation mutation


  Where a group of nucleotides become separated from the DNA sequence, and are then inserted into the DNA of a different chromosome
• Which mutations are most likely to have a significant impact and why

  ~Insertion, deletion, duplication and translocation

  ~Because they produce a frameshift, meaning the entire amino acid sequence produced will be different
• Which mutations are most likely to have a smaller impact and why

  ~Substitution and inversion

  ~Because they only alter one or very few triplets, the amino acid sequence might not be affected due to the degenerate nature of the genetic code
• Is a mutation resulting in a change to the amino acid sequence always harmful


  ~No as it may be neutral if the resulting change in proteins has no effect on the organism

  ~Also may be beneficial, which is the basis for evolution and natural selection
• What is a mutagenic agent


  Factors that increase the rate of gene mutation