Mad2 (Mitotic Arrest Deficient 2) is a member of the cell cycle checkpoint protein family, characterized by a core kinase binding domain. Mad2 is primarily located in the nucleus and near the spindle apparatus, playing a key role in the mitotic checkpoint signaling pathway by monitoring whether chromosomes are properly attached to the spindle. By blocking the cell's entry into the next phase of mitosis, Mad2 ensures the correct distribution of genetic material. Abnormal expression of Mad2 is associated with the development of various cancers, particularly as its overexpression or loss of function can lead to chromosomal instability.