cell cycle consists of the following: –g1 phase –s phase –g2 phase –m phase –cytokinesis

Cell Cycle

• Consists of the following:

–G1 phase

–S phase

–G2 phase

–M Phase

–Cytokinesis

Interphase• G1 phase

–Cell grows in size.

–Normal cellular activities occur.

–8-10 hours

Interphase

• S phase–Chromosomes

replicate. (DNA replicates)

–6-9 hours

Interphase

• G2 phase–Enzymes are synthesized.

–Cell growth continues.

–4-6 hours

Early Prophase

• Chromatin fibers shorten and condense.

• Chromatids are held together by a centromere.

Late Prophase• Nucleolus disappears.• Spindle forms. The

spindle extends from pole to pole.

• Asters radiate from spindle.

• Centrioles hold the spindle at each pole.

• Nuclear membrane disappears.

Metaphase

• Chromatid pairs line up along the equator of the cell.

Anaphase

• Centromeres split which separate the chromatids.

• Chromosomes move to opposite poles of the cell.

Telophase• Begins after

chromosomal movement stops.

• Spindle breaks down.

• Nucleolus reappears.

• Nuclear membrane reappears.

Cytokinesis• Not a part of

mitosis.

• Division of the cytoplasm.

• Cleavage furrow can form in late anaphase or early telophase.

Cancer

• Cells in body divide out of control.

• Excess tissue forms a tumor.

• Cancerous tumor is called a malignant tumor.

Types of cancer

• Most human cancers are carcinomas (arise from epithelial cells).

• Melanomas are cancerous growths of melanocytes.

Types of cancer

• Sarcoma is a general term for any cancer arising from muscle cells or connective tissues.

Causes of cancer

• Cause: Environmental agents called a carcinogen. Carcinogens induce mutations- change in the DNA sequence.

• Cancer-causing genes called oncogenes.

Treatments

• Chemotherapy: Drugs that are administered that poison cancer cells.

• Radiation destroys the chromosomes of cancer cells.

• Surgery is used to remove the tumor.

• Both chemotherapy and radiation can disrupt the function of normal cells.