∞ generated and posted on 2016.08.27 ∞

Phase during mitosis during which chromosomes become visible as seen through a light microscope.

Technically, during prophase the chromatin – the state that DNA is found in during interphase and as had been duplicated during S phase – is condensed to the form that chromosomes take during metaphase. Thus, sister chromatid pairs become visible during prophase as well as complete their condensation.

In addition to the formation of metaphase chromosomes during prophase, the nuclear membrane disappears and spindle fibers form. The latter are attached to two centrosomes and these centrosomes separate, moving towards opposite ends of the cell. Lastly, kinetochores assemble on chromosome centromeres, these interact with kinetochore microtubules, and chromosomes otherwise are jostled towards the metaphase plate.

This phase can also be differentiated into a prophase and prometaphase. Regardless of the name, the end point of the pre-metaphase aspects of mitosis is the lining up of chromosomes at the center of cells (on the metaphase plate) in anticipation of their movement away from the metaphase plate during anaphase.