Chromosome behaviour in

Chromatin condenses into visible chromosomes (each with two sister chromatids), the nuclear envelope breaks down, and the spindle apparatus begins to form from the centrosomes. Microtubules attach to the kinetochores of the sister chromatids.

The chromosomes line up along the metaphase plate (equator) of the cell, with each sister chromatid attached to a spindle fiber originating from opposite poles. This ensures equal distribution of genetic material.

Sister chromatids are separated and pulled to opposite poles of the cell by the shortening of spindle fibers. Each chromatid is now considered an individual chromosome.

The chromosomes arrive at the poles and begin to decondense. The nuclear envelope reforms around each set of chromosomes, and the spindle apparatus disappears. Cytokinesis usually occurs concurrently.

The nuclear envelope breaks down during prophase, allowing the spindle fibers to access the chromosomes. It reforms during telophase around the separated chromosomes, creating two distinct nuclei.

In animal cells, cytokinesis involves the formation of a cleavage furrow, a contractile ring of actin and myosin filaments that pinches the cell membrane inward, eventually dividing the cytoplasm into two daughter cells.

Plant cells form a cell plate, a new cell wall, between the two daughter nuclei. Vesicles containing cell wall material fuse at the midline, expanding outward until the new cell wall completely separates the two cells.