Cell Division

Mitosis and Cytokinesis

Cell Reproduction

• Interphase– Cell growth, DNA synthesis, Growth and

Preparation

• Mitosis (Division)– dividing the nucleus into two daughter nuclei

• Cytokinesis (Division)– separating the organelles and the cytoplasm

Mitosis

• Mitosis is a continuous process that can be observed in four stages: – Prophase– Metaphase – Anaphase– Telophase

Prophase 1• Chromosomes begin to condense• The nuclear membrane breaks down. • Spindle which is made up of several spindle

fibers form. – run at a right angle to the cell’s equator.

• An organelle called the centrosome helps assemble the spindle. – animal cells includes a pair of centrioles– centrosomes move to opposite poles of the cell

Metaphase• Chromosomes are packaged into their most

condensed form.

• Nuclear membrane is fully dissolved

• Chromosomes move to the center of the cell

• Spindle fibers form a link between the poles and the centromere of each chromosome.

Anaphase• Spindle fibers shorten

• Sister chromatids move toward opposite poles as the spindle fibers shorten.

• Each pole now has a full set of chromosomes.

Telophase• A nuclear envelope forms around the

chromosomes at each pole of the cell.

• Chromosomes now uncoil.

• The spindle dissolves.

• Mitosis is complete.

Cytokinesis• The cytoplasm is separated

• Two daughter cells are formed – Have half of the parent’s cytoplasm and organelles– Genetically identical diploid cells

• After cytokinesis, each cell enters the G1 stage of interphase.

Summary• The life of a eukaryotic cell cycles through;

– Growth, DNA replication– preparation for cell division – division of the nucleus and cytoplasm

• Mitosis is a continuous process that includes four stages: – Prophase– Metaphase – Anaphase– Telophase

• Cytokinesis– the cell membrane grows into the center of the cell and divides

it into two daughter cells– each daughter cell has about half of the parent’s cytoplasm and

organelles