Making copies of your cells... Cell Reproduction Making copies of your cells...
Chromosomes bodies of DNA and protein the DNA strand is tightly coiled around a chunk of protein if straightened out, the DNA strand would be 5 cm (2 in.) long each contains 2 “sister” chromatids joined by a centromere
Chromosomes
The Cell Cycle Sequence of growth and division Consists of two major phases: Interphase and Mitosis Cells spend most of their time in Interphase (about 95% of the time) Mitosis has four phases: Prophase, Metaphase, Anaphase, and Telophase
The Cell Cycle Interphase: DNA is copied and centrioles duplicate in preparation for mitosis time of rapid growth and metabolic activity
Mitosis: The phases Prophase: (first and longest) nucleus and nucleolus disappear, centrioles migrate to opposite ends of cell spindle fibers form
Mitosis: The phases Metaphase: (shortest) spindle fibers attach to centromeres chromosomes line up on the equator
Mitosis: The phases Anaphase: centromeres split and chromosomes are pulled apart each chromatid is now a separate chromosome
Mitosis: The phases Telophase: (last) cytokinesis occurs (cytoplasm pinches cell in half) chromosomes unwind, spindle breaks down, nucleus and nucleolus reform
Control of the cell cycle Even with 25 years of research, this is not fully understood What we know: enzymes monitor the cell’s progress from phase to phase if enzymes are produced at the wrong time or they are overproduced then they will cause uncontrolled dividing of cells= Cancer contact inhibition (or when the cells touch) will cause cells to stop growing unless the cells are cancerous
Cancer: what we know... Currently it is believed that cancer is caused by changes in the genes that control cell cycle enzymes Cancer cause tumors which deprive normal cells of the nutrients they need Eventually cancer cells invade the circulatory system and destroy major organs
Cancer: what we know... We think that cancer can be caused by either or both environmental and genetic factors Examples of environmental factors: UV radiation, cigarette smoke, air pollution, water pollution, and even viruses