f. the nuclear envelope begins to disintegrate. - chromatids separate at the beginning of this phase. d. the chromosomes line-up at the center of the cell. a. chromosomes arrive at opposite poles and begin to decondense. - the cell grows rapidly. - separate chromosomes are not clearly visible but the chromatin has become thicker and shorter. - a cell plate completely divides a plant cell. - kinetochores appear and mitotic spindle begins to attach to kinetochores. - each sister chromatid is attached to a spindle fiber from the opposite pole. - certain spindle fibers begin to elongate the cell.