Mitosis and the Cell Cycle: Phases Explained

Mitosis

• The smaller the cell the more efficient.
• Surface area to volume of a small cell is large. The larger ratio, the more efficient the cell.
• Mitosis is the division of the nucleus inside a cell.

Cells

• Cells must take in oxygen, water and nutrients but give off waste products such as carbon dioxide.
• Volume increases faster than surface area.
• The division of a cell is called cytokinesis.
• The cell will split into 2 daughter cells with identical DNA.

Chromosomes

• Each chromosome consists of two sister chromosomes
• Centromere- center of chromosome
• Chromatids- ends of chromosome
• Chromatin- substance of chromosome
• Histones- material that makes up chromosome
• Nucleosomes- DNA sequence combined around 8 histones
• Creation of a Chromosome= DNA-Nucleosome-Chromosome

Cell Cycle

• Interphase
• -G1, S, G2
• M-phase
• -Prophase
• -Metaphase
• -Anaphase
• -Telophase

Interphase

• Period between cell divisions
• G1- growing phase of cells
• S- DNA gets synthesized in cell
• G2- Organelles copy

M-phase (Mitosis)

• Mitosis- Division of the nucleus
• Cytokinesis- division of cytoplasm
• Prophase- centrioles begin to function, spindle fibers appear, nucleolus and nuclear membrane start to disappear
• Metaphase- chromosomes line up in center of cell, microtubules connect centromere to spindle fibers, asters arrange around each pole

M-phase (cont.)

• Anaphase- chromosomes split and move to opposite poles, this phase ends when chromosomes reach poles
• Telophase- chromosomes start to become chromatin, nuclear envelopes reforms, nucleolus reappears, spindle fibers break down, centrioles stop functioning.

Cytokinesis

• occurs in both animal and plant cells
• for animal cells, a cleavage furrow (indent) forms and the cells split
• for plant cells a vesicle and cell plates form as this separates the membrane and cell wall.

Cyclins

• Proteins that regulate the cell cycle are called cyclins
• cyclins regulate the timing of the cycle
• Internal regulators- proteins that respond to events inside cell
• External regulators- proteins that respond to events outside cell

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Cancers

• Benign- non-cancerous, can easily be removed
• Malignant- cancerous, not easily removed
• metastasis- spreading of cancers

Cell Cycle Image