Fact 1: Mutations may change the structure of a chromosome or just change a single nucleotide.

Fact 2: DNA is made up of nucleotides.

Given the two facts above, answer the question "What can change the structure of DNA?" with the following options: 
- Mutations
 - rays or beams
 - Genes
 - radiation
 - DNA
 - Smoking
 - Microscope
 - Chemicals


 

 Mutations        