The DNA has replicated but remains loosely coiled as chromatin, with the nuclear membrane intact to protect the DNA. The DNA then condenses to form chromosomes, the nuclear membrane and nucleolus disappear, and the spindle apparatus migrates to opposite poles. The spindle fibers then attach to the centromeres, aligning the chromosomes at the equatorial plate before shortening to split the centromeres and pull the chromosomes to the poles, after which the nuclear envelope reforms before the chromosomes uncoil.

1. Science September 2011 Mr. Swartz

2. DNA has replicated, but has not formed the condensed structure of chromosome. They remain as loosely coiled chromatin. Nuclear membrane still intact to protect the DNA molecules from undergoing mutation.

3. The DNA molecules progressively shorten and condense by coiling, to form chromosomes. The nuclear membrane and nucleolus are no longer visible The spindle apparatus has migrate to opposite poles of the cell.

4. The spindle fibers attach themselves to the centromeres of the chromosomes The fibers align the chromosomes at the equatorial plate.

5. All photographs from http://library.thinkquest.org/C0118084/Gene/Chromosomal_Inheritance/StagesMitosis.htm Slide Show created by Corina Carmona The spindle fibers shorten and the centromere splits The chromosomes reach the poles of their respective spindles. Nuclear envelope reform before the chromosomes uncoil. The spindle fibers disintegrate.