Cell Division Mitosis Chapter 10

Why do cells divide, rather than continually grow forever? The larger a cell becomes, the more demands the cell places of its DNA. The cell also has more trouble moving enough nutrients and wastes across the cell membrane.

Division of the Cell Before it becomes too large, a growing cell divides forming two “daughter cells.” The process by which a cell divides into new daughter cells is called cell division. Before cell division occurs, the cell replicates, or copies, all of its DNA. Thus, each daughter cell gets one complete set of genetic information.

Cell Division Cell division is complex and occurs in 2 main stages: Mitosis-division of cell nucleus Cytokinesis-division of cytoplasm Genetic information is carried by chromosomes. Before cell division each chromosome is replicated, or copied forming two identical sister “chromatids,” which will be separated from each other when the cell divides.

During the cell cycle, the following happens: The cell cycle is a series of events that cells go through as they grow and divide. During the cell cycle, the following happens: Cell grows (interphase) Cell prepares for division (interphase) Cell divides to form 2 daughter cells (each of which further divide) (cell division)

Events of the Cell Cycle Interphase G1 phase Cell grows (increases in size and makes new proteins and organelles) S phase Replication of chromosomes/DNA synthesized G2 phase Organelles and molecules needed for cell division produced.

Figure 10–5 Mitosis and Cytokinesis Section 10-2 Spindle forming Centrioles Chromatin Centromere Nuclear envelope Centriole Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Telophase Individual chromosomes Anaphase Nuclear envelope reforming

Mitosis (M phase) When the events of the G2 phase are completed, the cell is ready to enter the M phase and begin cell division. The events of mitosis are divided into four phases: Prophase Metaphase Anaphase Telophase

Prophase 1st phase of mitosis where: Centrioles take their place at opposite sides of the cell Spindle fibers form Chromatin coils to form chromosomes Nuclear envelope breaks down

Figure 10–5 Mitosis and Cytokinesis Section 10-2 Spindle forming Centrioles Chromatin Centromere Nuclear envelope Centriole Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Telophase Individual chromosomes Anaphase Nuclear envelope reforming

Metaphase The chromosomes line up across the center of the cell Each chromosome is connected to a spindle fiber at its centromere.

Figure 10–5 Mitosis and Cytokinesis Section 10-2 Spindle forming Centrioles Chromatin Centromere Nuclear envelope Centriole Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Telophase Individual chromosomes Anaphase Nuclear envelope reforming

Anaphase Sister chromatids separate into individual chromosomes and are moved apart

Figure 10–5 Mitosis and Cytokinesis Section 10-2 Spindle forming Centrioles Chromatin Centromere Nuclear envelope Centriole Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Telophase Individual chromosomes Anaphase Nuclear envelope reforming

Telophase The chromosomes gather at opposite ends of the cell and lose their distinct shapes. Two new nuclear envelopes will form.

Figure 10–5 Mitosis and Cytokinesis Section 10-2 Spindle forming Centrioles Chromatin Centromere Nuclear envelope Centriole Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Telophase Individual chromosomes Anaphase Nuclear envelope reforming

Cytokinesis The cytoplasm pinches in half. Each daughter cell has an identical set of duplicate chromosomes.

How will I ever remember the phases?

This is how you can remember the phases: Please Make Another Touchdown