  A Chevalley type integral basis for the ortho-symplectic Lie superalgebra is
constructed. The simple modules of the ortho-symplectic supergroup over an
algebraically closed field of prime characteristic not equal to 2 are
classified, where a key combinatorial ingredient comes from the Mullineux
conjecture on modular representations of the symmetric group. A Steinberg
tensor product theorem for the ortho-symplectic supergroup is also obtained.
