Puzzle title

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Across
  1. 6. The ability to develop an immunity to a chemical from a mutation.
  2. 7. A sudden change in a gene, trait, or segment of DNA.
Down
  1. 1. What DNA is made of.
  2. 2. An addition of one letter on the genetic code.
  3. 3. Mutation An exchange of one letter on the genetic code for another
  4. 4. A unit of heredity
  5. 5. these features support successful survival and reproduction in the new environment become more common; those that do not become less common