 Represents the longest time period of the cell cycle
 Busiest phase of the cell cycle
 G1: Cell grows in size and protein production is high
 S: Cell copies it’s chromosomes
 G2: After DNA is replicated organelles such as mitochondria are manufactured and cell parts needed for cell division are assembled.

Formation of sister chromatids
• Chromatin coils up and chromosomes become visible.
• Formation of sister chromatids held together by the centromere.
• Nucleus begins to disappear
• Nucleolus disintegrates.
• Centrioles begin to move to opposite ends of the cell. ( animal cells)
• Spindle begins to form - made from thin fibers of microtubules.
• In plant cells, spindle forms without centrioles.

aligning into the middle
 Shortest phase of mitosis
 Double chromosomes ( sister chromatids ) become attached to spindle fibers by their centromeres.
 Chromosomes pulled by spindle fibers to the middle of the cell.
 Each sister chromatid is attached by it’s spindle fiber that extends to the oppoosite pole.

Separation of sister chromatids
 Centromeres split apart.
 Chromatid pairs separate from each other.
 Pulled apart by the shortening of the microtubules in the spindle fibers.

 Begins when chromatids reach the opposite poles.
 Spindle breaks down
 Nucleolus reappears
 New nuclear envelope forms around each set of chromosomes.
 Lastly, a new double membrane forms between two new nuclei. This is called cytokinesis.

 Final stage of cell reproduction
 Division of the cytoplasm into approximately equal halves, resulting in a roughly equal distribution of organelles in each of the daughter cells.
 In cells lacking a cell wall occurs through a pinching inward
 Organisms with a cell wall undergo a process through which a so-called cell plate is built from the middle of the cell outward to the membrane.