How do mutations occur?

Types of Errors Made by DNA Polymerase

DNA polymerase can make different kinds of errors:

  • Mismatches: incorrect nucleotides are added, forming wrong base pairs (for example, A–C instead of A–T).
  • Slippage: the enzyme slips forward or backward along the DNA strand, causing insertions or deletions of nucleotides.
    If these errors are not corrected, they may become permanent mutations.