Isolated DNA Changes are Insufficient

• Compare mutations in the nucleotides of DNA with random changes to the letters of a book

• Can you improve a book by changing the letters in it at random?

• Must accept or reject all changes as a unit (as the changes are happening to one individual)

• • Therefore rate of change must be low (e.g. one letter per change to the book) or else an improper word will very likely form
  • E.g. changing a letter at random in each of five words is unlikely to result in five new proper words