Nuclear envelopes form around the chromosomes from fragments of the parent cell's nuclear envelope and portions of the endomembrane system. Chromatin fiber of each chromosome uncoils and the chromosomes become less distinct. Cytokinesis has begun and the appearance of two separate daughter cells occurs shortly after mitosis is completed. During prophase, the mitotic spindle forms in the cytoplasm from microtubules and associated proteins. Microtubules of the cytoskeleton are partially disassembled during spindle formation.
Spindle microtubules elongate by the adding tubulin subunits at one end.
Plant centrosomes lack centrioles. The centrosome replicates to form two centrosomes located just outside the nucleus. By the end of prometaphase, the two centrosomes are at opposite poles and the chromosomes have moved to the cell's midline. Each chromatid of a replicated chromosome develops its own kinetochore , a protein structure on the centromere. Some spindle microtubules attach to the kinetochores and are called kinetochore microtubules .