The term "no plus gene" refers to a genetic mutation where the organism lacks a functional copy of a particular gene. There are various synonyms for this term, including null allele, loss-of-function mutation, and knockout mutation. A null allele is a genetic variant where the gene function is completely abolished. Loss-of-function mutation is a genetic change where the gene activity is partially or completely disrupted, resulting in a loss or reduction of the gene's normal function. Lastly, a knockout mutation is a genetic modification in which the gene is entirely erased or inactivated. These synonyms are essential for geneticists and scientists to describe and study the effects of genetic mutations.