allelic series (multiple alleles)

codominance

complementation

complementation test

dominant negative mutation

double mutants

epistasis

essential gene

expressivity

full (complete) dominance

functional RNA

heterokaryon

incomplete dominance

lethal allele

modifier

multiple alleles

null mutation

one-gene-one-polypeptide hypothesis

penetrance

permissive temperature

pleiotropic allele

restrictive temperature

revertant

suppressor

synthetic lethal

temperature-sensitive (ts) mutations