Unit 1.6 - Mutations

• What are mutations?

  Changes in the DNA that can result in no protein or an altered protein being synthesised.
• Are mutations random or predicted?

  They are random and spontaneous but happen rarely.
• What are the two types of mutations?

  Single gene mutations and chromosome structure mutations
• What are single gene mutations?

  Changes or alterations that occur in a single DNA nucleotide sequence.
• What can single gene mutations result in?

  They can result in no protein or an altered protein being expressed.
• What happens in a substitution mutation?

  A single nucleotide is removed from a DNA sequence and replaced with another.
• What are the three types of substitution mutations?

  Missense, nonsense, and splice-site mutations
• What happens in a missense mutation?

  One amino acid is changed for another.
• What happens in a nonsense mutation?

  A codon that codes for an amino acid is changed to a stop codon. Polypeptide chain is stopped prematurely.
• What happens in a splice site-mutation?

  Some introns are retained and/or some exons are not included in the mature transcript during RNA splicing.
• What are two examples of frame-shift mutations?

  Insertion and deletion.
• What happens during insertion?

  An extra nucleotide is added into the sequence. This alters all the codons and therefore amino acids from the mutation onwards.
• What happens during deletion?

  A nucleotide is removed from the sequence. This alters all the codons and therefore the amino acid sequence from this point.
• Do frameshift mutations cause major or minor disruption?

  Major
• What can happen because of chromosome structure mutations?

  Death
• What happens in a chromosome deletion mutation?

  A section of a chromosome is removed.
• What happens in a duplication mutation?

  A section of a chromosome is added from its homologous partner
• What happens during a translocation mutation?

  A section of a chromosome is added to a chromosome that is not its homologous partner.
• What happens in an inversion mutation?

  A section of a chromosome is reversed
• Why are mutations important?

  They are the only source of new alleles in a population