Cell Cycle Mitosis and Cancer

What is the cell cycle? The cell cycle is the regular pattern of growth, DNA Replication, and cell division that occurs in eukaryotic cells. The stages of the cell cycle gets their names from early studies of cell division.

Cell Cycle Stages Stages in growth & division Interphase G1 Phase S Phase G2 Phase M Phase - Mitosis Cytokinesis

Interphase – “Resting Phase”

G1 Phase (Gap 1) Cell carries out normal functions Cell increases in size & organelles increase in numbers A cell spends most of its time in the stage Important checkpoint.

Synthesis (S) Phase Synthesis means to combine parts to make a whole. Copying of all of DNA’s instructions Chromosomes duplicated Human cells – 46 chromosomes double to 92.

G2 Phase (Gap 2) Second growth stage Time between DNA synthesis & mitosis Cell continues growing Needed proteins produced Important checkpoint

M Phase - Mitosis The division of the cell nucleus and its contents. Nuclear membrane dissolves, the duplication of DNA condenses around proteins and separates, and two new nuclei form. Cell’s energy used to make 2 identical daughter cells Stages Prophase, Metaphase, Anaphase and Telophase

Chromosomes condense at the start of Mitosis. A chromosome is one long continuous thread of DNA that consists of numerous genes along with regulatory information. Each chromosome consists of two identical “sister” chromatids. Each pair of chromatids is attached at an area called the centromere

Mitosis

Steps in Prophase DNA coils tightly & becomes visible as chromosomes Nuclear membrane disappears Nucleolus disappears Centrioles migrate to poles Spindle begins to form

Steps in Metaphase Spindle fibers from centrioles attach to each chromosome Cell preparing to separate its chromosomes Cell aligns its chromosomes in the middle of the cell

Metaphase

Steps in Anaphase Cell chromosomes are separated Spindle fibers shorten so chromosomes pulled to ends of cell

Anaphase

Steps in Telophase Separation of chromosomes completed Cell Plate forms (plants) Cleavage furrow forms(animals) Nucleus & nucleolus reform Chromosomes uncoil

Telophase        Plant             Animal

Cytokinesis Division of the cytoplasm Occurs after mitosis Forms two, identical daughter cells

Cytokinesis Cell Plate Forming in Plant Cells

How long does it take for cells to divide? Cell Type Time Fly Embryo 8 minutes Bacteria 20 minutes (Binary Fission) Human Skin 20-24 hours Human Nerve Cells Never once matured Human Liver 1 year Onion Cells 12 Hours

Cancer

Cancer The common name for the mutation of the cell cycle. Most cancer cell carry mutations, or DNA errors, in two genes that help make proteins involved in the cell cycle regulation.

DNA mutations disrupt the cell cycle. Mutations may be caused by: 1. radiation 2. smoking 3. Pollutants 4. chemicals 5. viruses

While normal cells will stop dividing if there is a mutation in the DNA, cancer cells will continue to divide with mutation.

Due to DNA mutations, cancer cells ignore the chemical signals that start and stop the cell cycle.

Due to DNA mutations, cancer cells cannot communicate with neighboring cells. Cells continue to grow and form tumors. Skin cancer

Treating Cancers Cancer treatments include “chemo” drugs that can stop cancer cells from dividing. For example, Taxol is a natural plant product; it works by inhibiting the spindle fiber formation and disrupting mitosis. Basically, stopping these cancer cells from dividing. Some drugs can cause an adverse affect on the human body. Any rapidly dividing cell, like gastrointestinal tract, hair and bone marrow cells can be “killed’.

SUMMARY Normal Cell Division DNA is replicated properly. 2. Chemical signals start and stop the cell cycle. 3. Cells communicate with each other so they don’t become overcrowded. Cancer Cells Mutations occur in the DNA when it is replicated. 2. Chemical signals that start and stop the cell cycle are ignored. 3. Cells do not communicate with each other and tumors form.

Links http://www.youtube.com/watch?v=Hm03rCUO Dqg http://www.youtube.com/watch?v=PwqY99gNi pE http://www.youtube.com/watch?v=VGV3fv- uZYI