18 months ago
Let me give it a try too :) -> : is_a
Mutation -> Variant
Polymorphism -> Variant
Mutation !<=> Polymorphism
Variant is the most general term, it refers to any genetic difference (e.g. sequence difference)
The other two terms refer to type and origin of the variation with respect to a population.
A mutation is a 'spontaneous' variation caused e.g. by a simple error in duplication, cell-division, strand-break, radiation, toxins, etc. It does not need to exist in the population, ancestry, or even the population of all cells in the organism. It is inheritable, if it affects the germ-line, but not necessarily inherited.
A polymorphism is a variation that exists in or becomes fixated within a population, e.g. if it is neutral or benefical. Therefore, at least two genotypes exist wrt. to the given variation/locus for which a prevalence can be assigned.
All existing polymorphisms must have started (some time ago) as a heritable mutation, but not all mutations become a polymorphism.
The orthogonal axis of the definition of variation is what is actually affected: from a single nucleotide, insertions/deletions, to chromosome re-arrangements.