The Cell Cycle

What is the Cell Cycle ? The sequence of growth and division in a cell is the Cell Cycle. Certain fly embryos have cell cycles that last only 8 minutes per cycle! Some mammals take much longer than that--up to a year in certain liver cells. Generally, however, for fast-dividing mammalian cells, the length of the cycle is approximately 24 hours.

What is the Cell Cycle ? The cell cycle includes interphase and mitosis. The cell spends most of its life in interphase.

Interphase means between phases. G1 (Growth 1) – Protein synthesis S (Synthesis) - DNA copies G2 (Growth 2) - Organelles double in number, to prepare for division centromere sister chromatids

Interphase means between phases.

Mitosis means the condition of threads. Mitosis takes place in cells in order for reproduction, growth, and repair. In single cells organisms, mitosis is the method of asexual reproduction. Mitosis is nuclear division plus cytokinesis. Mitosis in most cases produces 2 identical daughter cells during prophase, metaphase, anaphase, and telophase.

Mitosis means the condition of threads. Cells that do not undergo mitosis undergo apoptosis. Apoptosis, apo = from and ptosis = falling, is one of the main types of programmed cell death.

Mitosis means the condition of threads. Mitosis in a human body cell: 46 2n n = 23

Prophase: first phase Spindle forms Centrioles move to opposite poles Chromosomes become visible Nuclear membrane disappears

Metaphase: middle phase Chromosomes line up along the equator.

Anaphase: away phase Centromeres divide Chromatids separate and move to opposite poles

Telophase: far away Nuclear membrane forms around each group of chromosomes Chromosomes unwind

Cytokinesis: cell as individuals Animal: Cell pinches inward. Plants: A new cell wall begins to form

Cytokinesis

Identify the stages of the cell cycle on the following slides

Cancer and the Cell Cycle ? The cell cycle is controlled by proteins called cyclins and a set of enzymes that attach to the cyclin and become activated. If control of the cell cycle is lost, cancer can be the result. Cancer is a malignant growth resulting from uncontrolled cell division, which may be due to environmental factors or by changes in enzyme production.

Cancer and the Cell Cycle ? The production of enzymes is directed by genes which are located on the chromosomes. A gene is a segment of DNA that controls the production of a protein.

Cancer and the Cell Cycle ? Cancerous cells form masses of tissue called tumors that deprive normal cells of nutrients. In later stages, cancer cells enter the circulatory system and spread throughout the body, a process called metastasis, which ultimately disrupts the functions of organs, organ systems, and finally the organism.

Cancer and the Cell Cycle ? Cancer is the second leading cause of death in the U.S. exceeded only by heart disease. It can affect any tissue in the body. Lung cancer is the leading cause of death in the United States and kills 440,000 deaths each year.

Causes of Cancer Difficult to pinpoint because damage to genes could be a result of environmental factors (cigarette smoke, air and water pollution, exposure to UV rays, and viral infections) or genetic factors alone.

Cancer Prevention Healthy diet (low in fat, high in fiber content) Intake of certain vitamins and minerals (carotenoids, Vitamins A, C, and E, and calcium) Daily exercise No tobacco products