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Chapter 3.2Cell Division
Life Science
What causes organisms to grow??
Many organisms start as one cell…what happens to these cells?– Cells divide!! One becomes two, two
becomes four… Multi-cellular organisms grow because
of CELL DIVISION!
Cell Division Cell Division- increases the total
number of cells and causes multi-cellular organisms to grow and develop.
3 Functions:
1. Growth
2. Development
3. Repair
The Cell Cycle Cells contain periods of formation,
growth and development, and death called a life cycle.– Forms, Grows/Develops, Dies.
The length of the cycle depends on the type of cell.
CELL CYCLE: Page 81
cell grows and carries out normal activities; organelles duplicate
DNA replicates and chromosomesduplicate
cell grows and prepares for mitosis
Mitosis
Mitosis (mi TOH sus) – process in which the nucleus divides to form two identical copies of cellcopies of cell.
Do YOU remember the steps or
phases of Mitosis?
BEFORE MITOSISInterphase
Interphase - phase where Eukaryotic cells spend most of their “life”– A period of growth and development.
– Cell duplicates its chromatin and prepares for cell division.
Cell is not dividing***
Chromatin, Chromatid, Chromosome …
MITOSIS BEGINSProphase
Prophase “P” for Pairs– Nucleus disappears– Centrioles - two small structures that
move to opposite ends– Spindle fibers - (threadlike) begin to
stretch across the cell.
Metaphase Metaphase- “M” for
Middle– Chromosomes line up across the center
of the cell – Spindle Fibers attach to the centromere.
Anaphase
Anaphase- “A” for Apart– Centromere divides – Chromatid Pairs separate and moves to
opposite ends of the cell– Spindle Fibers pull similar to a fishing rod
Telophase Telophase- “T” for Two
– Spindle Fibers disappear
– New Nucleus is formed (nuclear membrane)
– Two Cells form.
AFTER MITOSIS Cytokinesis- the division of the parent
cell’s cytoplasm.
(Page 85) In animal cells, the cell is pinched
into two identical daughter cells.
http://www.cellsalive.com/mitosis.htm
Results of Mitosis Each cell in your body (except sex
cells) has the same number of 46 chromosomes (23 pairs)
Allows growth and replaces damaged cells