Term: suppressor: a gene that suppresses the phenotypic expression of another gene (especially of a mutant gene)
Broader: gene: (genetics) a segment of DNA that is involved in producing a polypeptide chain; it can include regions preceding and following the coding DNA as well as introns between the exons; it is considered a unit of heredity | Unrelated: foreword: a short introductory essay preceding the text of a book