Task: Sentence Ordering
Input (English): Steps: (1) In this stage the chromosomes become visible and the centrioles separate and move to opposite poles of the cell (2) In prophase the chromosomes become visible and the centrioles separate and move to opposite poles of the cell (3) In metaphase the chromosomes line up across the center of the cell and become connected to the spindle fiber at their centromere (4) In anaphase the sister chromatids separate into individual chromosomes and are pulled apart (5) During telophase the chromosomes gather at opposite ends of the cell and lose their distinct rod-like shapes (6) Two new nuclear membranes then form around each of the two regions of DNA and the spindle fibers disappear.  
Where does the following step fit into the given list of steps: Prophase is the first and longest stage of mitosis 
Output (English):  Before step 1.