Biology Mutations

• What is the definition of a mutation?

  A change in the DNA base sequence
• What is an example of a mutation in DNA?

  A change from C to G in the DNA sequence
• When do mutations commonly occur in cells?

  During DNA duplication before cell division
• What are two factors that increase the risk of mutations?

  Carcinogens and certain types of radiation
• How do carcinogens affect mutations?

  They increase the risk of a mutation occurring
• What is a gene?


  A section of DNA that codes for protein
• What is a triplet or codon in DNA?


  A group of 3 bases that codes for an amino acid
• How many different amino acids can be coded by codons?


  20 different amino acids
• What happens if a mutation changes a codon?


  The amino acid that it codes for might change
• How can a mutation affect protein function?

  It can change the shape or function of the protein
• What is the effect of a mutation on an enzyme's active site?

  It may change the shape so the substrate can't fit
• Why do most mutations not have significant effects?

  They often only affect a protein very slightly
• What is non-coding DNA?


  DNA that isn't part of any gene and doesn't code for protein
• What role does some non-coding DNA play?


  It can play an important role in the expression of genes
• Why might a nerve cell not produce hemoglobin?


  Because the gene for hemoglobin is switched off
• What are the three specific types of mutations?

  • Substitution mutations
  • Insertion mutations
  • Deletion mutations
• What is a substitution mutation?


  When one of the bases is changed or substituted for another
• How does an insertion mutation affect the DNA sequence?


  An extra base is inserted, shifting subsequent bases
• Why are insertion mutations considered worse than substitution mutations?


  They alter all subsequent codons and amino acids
• What is a deletion mutation?


  When one of the bases is deleted from the sequence
• What happens to the DNA sequence after a deletion mutation?


  All subsequent bases shift one space to the left
• What are the consequences of mutations on proteins?


  • Change in amino acid sequence
  • Potential change in protein shape and function
  • Possible loss of enzyme activity
  • Most mutations have minimal effects