Download Mitosis and Cell Division Notes

Name: _______KEY_____________________________
Date: _____________
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Cell Growth and Division
DNA
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DNA – Deoxyribonucleic Acid
DNA is the genetic material inherited from parents
DNA Structure
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Double Helix
Which is basically a twisted ladder shape
The “side” of the ladder is a Sugar-phosphate backbone
The “rungs” are nitrogen bases
DNA—Nitrogen Bases
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4 Different Nitrogen Bases
G – Guanine
C – Cytosine
A – Adenine
T – Thymine
G only pairs with C
A only pairs with T
DNA in Humans
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Humans have 23 pairs of chromosomes in each body cell
Or 46 chromosomes per body cell
Humans have 23 individual chromosomes in each sex cell (sperm or egg)
Mitosis only occurs in body cells
Interphase - the stage between cell divisions
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DNA is in a thin, elongated shape called Chromatin
Chromatin duplicates and grows
Chromatin begins to condense but is not visible
Cells spend most of their life in interphase
Mitosis – 4 Phases
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1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
The goal of mitosis is to create two identical nuclei
Prophase
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Chromatin coils to form Chromosomes
Chromosomes are connected by a Centromere
Nuclear Membrane breaks down
Centrioles move to opposite ends of the cell
Spindle fibers form connecting Centrioles to Centromeres
Metaphase
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Chromosomes line up in the middle of the cell
Anaphase
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Centromeres split and the Chromosomes divide
Spindle Fibers shorten and the Chromosomes are drawn toward the Centrioles
Telophase
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In many ways the opposite of Prophase
Chromosomes uncoil
Nuclear Membranes form around each new Nucleus
Spindle Fibers breakdown and disappear
Cytokinesis—Cell Division
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Animal Cell – cell membrane pinches in from the outside to form two new Daughter Cells
Plant Cell - a cell plate forms in the middle of the cell, then grows outward to form part
of the cell wall and two new daughter cells
Why does Mitosis and Cytokinesis happen?
1. Healing
2. Growth