mutations

• what is a gene mutation

  A change in the base sequence of DNA
• what are the two types of error that can cause a mutation

  substitution

  deletion
• What is a substitution mutation?

  Replacement of a single base by another nucleotide
• what is a deletion mutation

  one base is taken away from a gene or DNA sequence
• what is the effect of a mutated gene

  changes the order of bases which code for amino acids so changes the amino acid sequence for a protein which can alter the protein made
• what is a point mutation and how does it effect the gene sequence

  mutation that occurs from substitution

  only effects one triplet
• what are the threee types of point mutation

  silent

  nonsense

  missense
• What is a silent mutation?

  alters a base but does not change the amino acid
• why does changing a base not always change the amino acid coded for e.g silent mutations


  dna is degenerate- more than one triplet codes for the same amino acid
• what is a nonsense mutation?

  change of a base to prematurely form a stop codon
• why are nonsense mutations bad


  - the poly peptide chain is incomplete

  - protein chant form

  - cause form a non functioning enzyme
• what is a conservative missense mutation?


  mutation results in a different aa encoded, but that new aa is similar in chemical structure to the original code
• what is a non conservative missense mutation

  Occurs when the mutated amino-acid does not share the same properties as the unmutated amino-acid

  - changes the polarity - bonds form differently - different protein structure
• what is a frame shift mutation and how does it effect the gene sequence

  mutation occurs by deletion or insertion of a base

  pushes the entire base sequence either to the left (deletion) or to the right (insertion)
• what is a mutagenic agent

  Something that increases the rate of mutations in DNA.
• examples of mutagenic agents (physical, chemical and biological)

  x-rays, UV light (physical),

  nitrous acid (chemical)

  some viruses (biological agents)