PHASES OF MITOSIS Biology Fall 2016 THE PHASES

PHASES OF MITOSIS Biology Fall 2016

THE PHASES OF MITOSIS • Mitosis is a continuous process. • Biologists have divided the mitotic phase into 4 main stages: 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase

PROPHASE • This is the first and longest phase. • The chromatin bundles up to form chromosomes in the nucleus. • Each chromosome consists of a pair of sister chromatids. • Sister chromatids are joined at the centromere.

CHROMATIN

CHROMOSOMES

CENTROMERE

PROPHASE • The chromosome duplicates during INTERPHASE. • The nucleolus disappears. • Cells stop making ribosomes and a football shaped structure called the mitotic spindle (aka spindle fibers) forms. • The spindle fibers start tugging chromosomes toward the center of the cell.

METAPHASE • This is a brief, second phase of mitosis. • The chromosomes are pulled toward the center of the cell. • Spindle fibers pull the centromere and align the chromosomes at the equator of the cell.

ANAPHASE • The third stage of mitosis. • The spindle fibers begin to shorten. • The sister chromatids separate. • Each chromatid is now considered a “daughter”. • Spindle fibers begin to shorten, puling the split chromatids to opposite poles of the cell.

TELOPHASE • Final stage of mitosis • Chromatids move to opposite sides of the cell. • Two new nuclei are formed- one on each side of the cell. • Two daughter cells are formed when a new double membrane forms. • This allows the cytoplasm to divide by CYTOKINESIS.

TELOPHASE • The final stage of mitosis • A complete set of identical chromosomes is positioned at each pole of the cell. • The nuclear membranes start to reform. • The chromosomes begin to uncoil. • The spindle fibers fall apart.

MITOSIS IN REAL TIME