Electronic systems and methods of operating memory devices are provided. In one such embodiment, a memory device receives an external address that addresses a non-defective column of memory cells of a sequence of columns of memory cells of the memory device in place of a defective column of memory cells of the sequence of columns of memory cells such that the non-defective memory column replaces the defective memory column. The non-defective column of memory cells is proximate non-defective column of memory cells following the defective column of memory cells in the sequence of columns of memory cells that is available to replace the defective column of memory cells.