oligogene

noun

oli·​go·​gene ˈäl-i-gō-ˌjēn  ə-ˈlig-ə- 

: a gene that exerts a major effect on a character either as one of two Mendelian alternatives or as one of a few genes controlling a qualitative character

oligogenic

ˌäl-i-gō-ˈjen-ik  ə-ˌlig-ə- 

-ˈjē-nik

adjective