it refers to gene or mutation that has multiple effects like polyphenotype

Pleiotropy refers to a case where one gene may influence several other characteristics. An example of pleiotropy is sickle cell anemia, a disorder in which a single point mutation in the amino acid sequence for hemoglobin results in a spectrum of effects. Red blood cells produce abnormal hemoglobin molecules, which, because of their odd shape, tend to stick together and crystallize. Therefore, the normal disk shape of red blood cells changes to a sickle shape (hence the name of the disorder). Sickle-shaped red blood cells will clog small vessels, causing pain and the possibility of brain damage and heart failure. Since some of the hemoglobin in these cells is abnormal, there is less oxygen available, leading to physical weakness and anemia. If left untreated, the anemia can impair mental function.