mutations

• What is a mutation?

  any change in the DNA sequence
• What is a gene mutation?

  a change in the base sequence of a gene and can happen spontaneously during DNA replication
• Examples of gene mutation

  base substitution and deletion
• What is a base substitution mutation?

  A single replacement of one nucleotide for another which contains a a different base

  • potentially coding for a new amino acid and disrupting polypeptide chain
• Why do not all base substitutions impact the sequence of amino acids?

  due to the degenerate nature of the genetic code, where many triplets code for the same amino acid, and so depending on which base changes, there may be no impact.
• What is base deletion?

  One or more nucleotides get deleted from the DNA sequence (result in a frameshift mutation)Often has significant effect on encoded protein because it can alter the sequence of all the codons following the lost base.
• What is a chromosome mutation?

  a change in the structure or number of chromosomes
• Examples of chromosome mutation?

  1. change in whole sets of chromosome

  • when organisms have three or more sets of chromosomes rather than the standard pair

  2) change in number of individual chromosomes

  • when homologous pairs fail to separate during meiosis (non dysjunction) leading to an organism having 1 more or 1 less chromosome