Phases of Mitosis

Anaphase

Anaphase is the third phase of mitosis. It begins when sister chromatids suddenly separate and begin to move apart. Once anaphase begins, each sister chromatid is now considered an individual chromosome. During anaphase, the chromosomes separate and move along spindle fibers to opposite ends of the cell. Anaphase comes to an end when this movement stops and the chromosomes are completely separated into two groups.

Telophase

Following anaphase is telophase - the fourth and final phase of mitosis. During telophase the chromosomes, which were distinct and condensed, began to spread out into a tangle of chromatin. A nuclear envelope reforms around each cluster of chromosomes. The spindle begins to break apart, and nucleolus becomes visible in each daughter nucleus.

Prophase

The first phase of mitosis, and is usually the longest; may take up to half of the total time required to complete mitosis. During prophase, the genetic material inside the nucleus condenses and the duplicated chromosomes become visible. Outside the nucleus a spindle starts to form. The duplicated strands of the DNA molecule can be seen to be attached along their length at an area called the centromere. Each DNA strand in the duplicated chromosome is referred to as a chromatid or sister chromatid. When the process of mitosis is complete, the chromatids will have separated and been divided between the new daughter cells. During prophase, the cell starts to build a spindle, a fanlike system of microtubules that will help to separate the duplicated chromosomes. Spindle fibers extend from a region called the centrosome. Where tiny paired structures called centrioles are located. Plant cells lack centrioles, and organize spindles directly from their centrosome regions. The centriolles, which were duplicated during interphase, start to move toward opposite ends, or poles, of the cell. As prophase ends, the chromosomes coil more tightly, the nucleolus disappears, and the nuclear envelope breaks down.

Metaphase

This is the second phase of mitosis, generally the shortest. During metaphase, the centromeres of the duplicated chromosomes line up across the center of the cell. Spindle fibers connect the centromere of each chromosome to the two poles of the spindle.