Download Honors Biology Cell Division Mitosis

Honors Biology
Cell Division
Mitosis
Spring 2009
• Mitosis – division process that occurs in
almost all body cells
• Result- from one “mother” cell, two
identical “daughter” cells are produced
• Uses – repair, growth, maintenance
• Process divided into stages
• Smooth, flowing process with each stage
having early, mid and late steps
Mitosis Process
Interphase
“Between” division stage
Cell is “getting ready” to divide
Doing “cell work”
** Chromosomes duplicate during
this stage
How many chromosomes present in
a human cell?
46
What is really duplicating? How?
Important Cell Parts for Interphase:
Nucleus, nucleolus, centrioles,
chromatin
Chromosomes
Chromosomes are in
homologous pairs – same
basic size and shape, same
basic genes at same basic
loci
Locus = gene location
Why two of each?
How many pairs in a human
cell?
23 pairs = 46 total
Cells called Diploid when
chromosomes are in pairs
Duplicated Chromosomes
DNA/chromosomes duplicate
How?
Called: Sister Chromatids
Held together by a
centromere
Now, how many
chromosomes in a
human cell?
92
“Direction” on a cell
Equator –
center
Poles – two
ends
Prophase
Sister Chromatids thicken and
become visible from chromatin
Nuclear membrane and nucleolus
“disappear”
Centrioles duplicate and move to
poles
Spindle fibers grow from centrioles
Still, 92 chromosomes
Metaphase
Sister Chromatids line
up on equator in a line,
two abreast
Spindle fibers grow to
attach to centromeres
Entire set-up called the
spindle
Still, 92 chromosomes
Anaphase
Centromere splits and chromatids
move to the poles
Still, 92 chromosomes; 46 at each
pole
Telophase – Animal Cells
Nucleolus and nuclear
membrane reform
Chromatids unravel into
chromatin
Spindle fibers disappear
Cleavage furrow pinches the
mother cell into two daughter
cells
Cytokinesis = final division of
the cell cytoplasm
How many chromosomes in
each daughter cell?
46 chromosomes at each pole
2 Diploid Cells?
Telophase – Plant Cells
What is different about
plant cells?
No spindle
Why not?
No centrioles
Cell plate grows across to
divide the cells
Mitosis in Summary
Onion Root Tip Mitosis
Onion Root Tip Cell Mitosis
Onion Root Tip Mitosis
Stage of Mitosis?
Stage of Mitosis?
Stage of Mitosis?
Stage of Mitosis?
Cell Cycle
• Life cycle of a
cell
• Consists of
various
stages/phases
Cell Cycle
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Most of a cell’s life is spent in Interphase
Mitosis is a very small part of its life
Interphase divided into stages
G1 occurs right after cytokinesis of mitosis
G=?
Growth of daughter cells occur
Near the end – cellular contents (organelles,
proteins, lipids, etc.) are duplicated
G0 Stage
•
•
•
•
•
•
Some cells enter from G1 to G0
Never duplicate cell organelles
Never do mitosis
Just become functioning cells
Examples?
Human muscle cells, some
nervous cells, red blood
cells
•
•
•
•
S Phase
S=?
Synthesis Phase
Chromatin (Chromosomes) duplicate their
DNA
• Chromosome number?
• Goes from 46 to 92
• G2 Stage
• Cells continue to grow
• Chromosomes may run a “spell check”
to look for errors in DNA
• Can even make some repairs
•
•
•
•
M phase
M=?
Mitosis phase
Cell completes all
stages of mitosis
• Smallest portion of a
cell’s life cycle (brown)
• All in (pink/blue) =
Interphase
Cancer
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•
•
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•
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Cancer is “out of control” mitosis
One mother cell may form more than two daughter cells
A daughter cell may have multiple nuclei
Mitosis is so rapid it often forms masses or tumors
(lesions)
Masses are capable of causing blood vessels to grow
into them to provide blood
Chemotherapy (drugs) or radiation are meant to kill
cancerous (malignant) cells
Often kill normal cells also = negative side effects
Noncancerous tumors = benign
Photos of Cancerous Tumors
• Brain Cancer
More Photos
• Liver
Cancer
More Photos
• Skin
Cancer
Photos of Cancerous Tumors
Breast Cancer