The gene which exhibits multiple effects is known as a pleiotropic gene. Pleiotropy is the phenomenon where a single gene influences multiple traits or phenotypes. This means that a change or mutation in this gene can have widespread effects on various aspects of an organism`s development or physiology. Option 1, pseudogene, refers to a non-functional copy of a gene. Option 3, complementary gene, refers to a gene that interacts with another gene to produce a specific phenotype. Option 4, polygene, refers to a group of genes that collectively contribute to a particular trait. Therefore, the correct answer is option 2, pleiotropic, as it accurately describes a gene that has multiple effects on an organism.