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Cell Division
By Mr. Kauffman
Outline
• Cells Review
• What is cell
division?
• The Cell Cycle
• Interphase
• Mitosis
• 4 Steps of Mitosis
• Results of Mitosis
•
•
•
•
Meiosis
8 Steps of Meiosis
Results of Meiosis
2 Types of Cell
Division
Cells Review
• Cell: smallest part of any
living thing that carries out
the functions necessary to
support life
• Unicellular organism: living
thing made up of 1 cell
• Multicellular organism: living
thing made up of many cells
What is cell division?
• Cell division: a way to
produce more cells
– Usually 1 cell divides to make 2
cells
• Why is cell division important
to multicellular organisms?
Cancer cell dividing
– Its how they grow
– Replace cells that have died
• Why is cell division important
to unicellular organisms?
– Its how they reproduce
E. Coli cell dividing
The Cell Cycle
• Cell cycle: everything
that happens from 1
cell division to the next
– 2 parts
1. Interphase
2. Mitosis
Interphase
• Interphase: longest
part of the cell cycle
– The cell prepares to
divide
• It grows in size
• It copies its DNA
Mitosis
• Mitosis: Part of the cell cycle
when the cell actually
divides to form 2 identical
cells
– Produces normal body cells
• Skin and muscle cells
– The cells produced are
identical to each other and to
the original cell
Mitosis
• Mitosis has 4 steps:
1) Prophase
2) Metaphase
3) Anaphase
4) Telophase
4 Steps of Mitosis
1. Prophase
– 1st step
– Nucleus disappears
– Chromosomes form
in nucleus (look like
X’s)
•
•
These are how the
DNA is stored in our
cells
Humans have 46
single chromosomes
(23 pairs)
4 Steps of Mitosis
2. Metaphase
– 2nd step
– Chromosomes
are lined up in
the middle of the
cell
4 Steps of Mitosis
3. Anaphase
– 3rd step
– Chromosomes
are pulled apart
– ½ of each
chromosome
goes to each end
of the cell
4 Steps of Mitosis
4. Telophase
– 4th step
– Cytoplasm begins
to pinch in at
center of cell
– Eventually the 1
cell splits to form
2 cells
•
Each new cell has
its own nucleus
and set of DNA
Results of Mitosis
• Mitosis produces
normal cells in the
body
– Skin and muscle
cells
• 1 cell splits to form 2
cells
– The new cells are
identical to each
other
– The new cells are
also identical to the
original cell
Meiosis
• Meiosis: cell division
that produces
reproductive cells
– Reproductive cells are
also called gametes
– 2 basic types of gametes
(reproductive cells)
• Females – egg cells
• Males – sperm cells
Why Meiosis is Needed
• Fertilization: combining of sperm and egg cells
to form a zygote
– the zygote then grows and develops into a new
organism
– how living things reproduce sexually (combining of 2
cells)
Meiosis
• Meiosis has 8 steps
– Basically goes through
mitosis twice
– There are 2 cell
divisions
Meiosis
• 8 Steps of Meiosis:
– Prophase 1
– Metaphase 1
– Anaphase 1
– Telophase 1
– Prophase 2
– Metaphase 2
– Anaphase 2
– Telophase 2
Results of Meiosis
• Meiosis produces
reproductive cells (gametes)
– Sperm and egg cells
• 1 cell splits to form 4 cells
– The 4 new cells have ½ of
the DNA that the original cell
had
– Haploid cells: cells with ½ of
the amount of DNA of a
normal cell
– Diploid cells: cells with the
normal amount of DNA
2 Types of Cell Division in Humans
Mitosis
Characteristics
Meiosis
Normal body cells
Reproductive cells
4
Types of cells
produced
# of steps
PMAT
Step names
PMAT (1 and 2)
2
# of cells produced
4
46 (single)
# of chromosomes
in cells
Comparison to
original cell
23 (single)
Identical
8
½ the DNA
2 Types of Cell Division in Humans