Final answer:
The different forms of bases, which have to do with keto versus enol and amino versus imino groups that are attached to the bases, are called tautomers.
Step-by-step explanation:
The different forms of bases, which have to do with keto versus enol and amino versus imino groups that are attached to the bases, are called tautomers. Tautomers are isomers of a compound that readily interconvert by a chemical reaction called tautomerization. Keto and enol tautomers involve the reversible migration of a hydrogen atom and a double bond, while amino and imino tautomers involve the reversible migration of a hydrogen atom and a nitrogen atom.