There are different theories about the origin of dragons: some say the ancient ancestor of all dragons was a creature called the Protodragon, the first creature developing magic, with a snake shape. Some others believe that all dragons originate from Galaxy Dragons, and the galaxy dragons originate from supernovas. There are also some other theories.
All dragons have magic. . Magic is what makes a dragon a dragon; a dragon's powerful magic separates it from non-dragons. Done Witches (fictional) possess powerful magic too, but are not classified as dragons (not even fictional dragons) because they use their magic in spells unlike dragons.
A dragon's elements are the kinds of magic they primarily contain. A dragon may contain trace elements of magics they are not aligned with, possibly from their evolutionary history. A dragon may have up to 4 elements in its magical makeup, but combinations of more than 4 elements are unstable.
Breeding and Heredity
Dragons are creatures governed by magic, and thus heredity works differently than it does for other living things. In the wild dragons usually mate and breed with other dragons of their kind, but some dragons, like Frostfire Dragons and Crystal Dragons may hybridize with other dragons.
Wizard Manipulation of Breeding Magic
The wizards have learned to manipulate breeding magic to change a dragon's natural breeding times and combinations, and allow dragons to breed with other dragons whenever the wizards want, and genders are not a problem as the Breeding Cave mixes the magic of dragons rather than making them actually mate. This enables parks to breed rare dragons. For every different dragon species to be bred in parks, a spell must be casted. Dragons have to be studied to find out how the spell must be casted, and the wizards are unable to decide themselves which dragons are required and how rare the dragon is, this depends on the dragon itself.
Dragons form magical bonds with wizards. This is a relationship of mutual respect and loyalty to the point of death. Wizards get most of their magic from the dragon they form a bond with, and a wizard's magic will be the same kind as that of the dragon they are bonded to.