When two events (call them A and B) are Mutually Exclusive it is impossible for them to happen together: P(A and B) = 0. The probability of A and B together equals 0 (impossible).
Answer Wiki. Strauss & Howe, the social historians known for pioneering generational theory[1], would say that Gen X (the 13th generation) and Gen Y (the millennial generation) each have the traits of their corresponding generational archetypes. Generation X is generally used to refer to people born in the 60s and 70s. According to Strauss & Howe, it is a Nomad generation, an archetype they share with the Lost Generation of the 1890s and 1900s. Both generations are characterized by a disaffected attitude and general disdain for everything that came before.
XX/XY sex chromosomes. The XX/XY sex-determination system is the most familiar, as it is found in humans. The XX/XY system is found in most other mammals, as well as some insects. In this system, most females have two of the same kind of sex chromosome (XX), while most males have two distinct sex chromosomes (XY). The X and Y sex chromosomes are different in shape and size from each other, unlike the rest of the chromosomes , and are sometimes called allosomes.