Transcript CELL DIVISION intro

CELL DIVISION
Mitosis and Meiosis
Why do cells have to divide?
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Demonstration
3 reasons cells must divide
1) Replace damaged or dead cells
2) Growth
3) Surface area to volume ratio
What is cell division?
• Cells replicate themselves
• Rates of division
1) Bacteria: 20 minutes
What is cell division? (cont.)
• Rates (cont)
2) Average body cell (ex: lining of esophagus,
or skin cells): about 24 hours
Rates of Division (cont.)
3) Red Blood Cells- Do not divide, but has a life
span of about 180 days. Made in the bone
marrow.
Rates of Division (cont.)
4) Nerve cells= Do not divide
The Cell Cycle
2 main parts
of the cell
cycle:
1) Interphase
2) Mitosis
Part 1: Interphase
• G1 = The cell grows, doubles in size, and
doubles the number of organelles
• S = Synthesis of DNA, replication of DNA
happens
• G2 = Second growth phase, prepares for
division
Part 2: Mitosis
• The cell divides by going through the
following phases:
• P. M. A. T. Then cytokinesis
• P= Prophase
• M= Metaphase
• A= Anaphase
• T= Telophase
Interphase (before mitosis)
• DNA is copied. The two sets of DNA are
condensed into Chromosomes that are
connected at the center (the centromere).
These are known as “sister chromatids”
Prophase
• Cell division begins. Centrioles form at
either end of the cell and begin to form
spindle fibers
Centriole
Metaphase
• Sister chromatids attach to the spindle
fibers
Centriole
Anaphase
• Sister chromatids separate and begin to
move towards the centrioles at either end
of the cell.
Telophase
• The separate chromatids are surrounded
by a new nuclear membrane forming a
new nucleus with a complete set of DNA.
Cytokinesis
• The cell membrane moves inward to
create two new cells.