Ch. 10, Cell Growth and Division Ch. 11, Meiosis (sec. 11-4)

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Ch. 10, Cell Growth and DivisionCh. 11, Meiosis
(sec. 11-4)

• Ch. 10
• Cell Growth- why do cells divide instead of
  continue to grow?
• Cell Division Cell Cycle and when a cell
  divides, Mitosis
• Regulation of the Cell Cycle- how its
  controlled, what happens when its out of control
• Ch. 11
• Phases of Meiosis
• Comparing Mitosis and Meiosis

2
Cell Growth
Section 10.1 Cell Growth
Im out of control!
Too Big!
Just right
TooSmall

• How do organisms grow? Do their cells get
  bigger? Or do they make more cells?
• Answer Make more cells!!!
• There is a limit to how big cells can grow!
• Getting bigger does 2 things
• Places more demands on DNA
• Makes it harder to move molecules across a cells
  membrane

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Surface Area to Volume Ratio
Bigger is NOT better!
Volume (V) 1 x 1 x 1 1 cm3 (length x width x
height)
More surface area! Good!
Ratio of SA to V 6/1 61
SA 3 x 3 x 6 54 cm3
Less surface area! Bad!
V 3 x 3 x 3 27 cm3
Ratio of SA to V 54/27 21
4
Whats the solution to this traffic problem?
5
Cell Division
Im too fat
daughter
daughter
Mommy?

• When a cell divides, the 2 cells that result are
  called daughter cells
• Cell Division process by which a cell divides
  into 2 new daughter cells
• Before cell division, the cell replicates, or
  makes copies of all of its DNA
• Solves the 2 problems with cell growth
• New daughter cells get one complete set of
  genetic information- they get their own complete
  genetic library
• No more problems with SA to V ratio because
  daughter cells has an increased ratio of SA to V
  because their volume overall is reduced (one cell
  dividing into two makes both cells smaller)

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Cell Division
Section 10-2

• In Eukaryotes (you!), cell division occurs in 2
  main stages
• Mitosis division of the cells nucleus
• Cytokinesis division of the cytoplasm

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(Sy-toh-kih-NEE-sis)
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Chromosomes
chromatid

• When a cell isnt in the process of dividing,
  chromosomes are not visible because they are
  spread out within the nucleus.
• However, when cell division is beginning, the
  chromosomes condense into compact, visible
  structures we can see in a microscope.
• Before cell division occurs, each chromosome is
  copied, or replicated, and the identical copies
  are called sister chromatids (KROH-muh-tids)

replication
Yo! Sis!
LYLAS!
Centromere
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Sister chromatid
Sister chromatid
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The Cell Cycle
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• The Cell Cycle is a series of events that cells
  go through as they grow and divide
• 1. Cell grows
• 2. Cell prepares for division
• 3. Cell divides to form 2 daughter cells (each
  daughter cell will begin the cell cycle again)

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Cell Cycle Phases
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I
G1 phase
I
M
M phase
S phase
I
G2 phase
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Mitosis

• Interphase then.
• Mitosis has 4 phases
• 1. Prophase
• 2. Metaphase
• 3. Anaphase
• 4. Telophase

I then ..PMAT
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Interphase is NOT part of Mitosis!!!!! Remember
that!
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Mitosis
Interphase cell grows and replicates its DNA
and centrioles.
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Interphase
Centrioles
Chromatin
Nuclear envelope
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Interphase cell grows and replicates its DNA
and centrioles.
Prophase chromatin condenses into chromosomes,
centrioles separate, spindle forms, nuclear
envelope breaks down
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Interphase
Spindle forming
Prophase
Centrioles
Centromere
Chromatin
Nuclear envelope
Chromosomes (paired chromatids)
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Prophase chromatin condenses into chromosomes,
centrioles separate, spindle forms, nuclear
envelope breaks down.
Interphase cell grows and replicates its DNA
and centrioles.
Interphase
Spindle forming
Prophase
Centrioles
Centromere
Centriole
Chromatin
Nuclear envelope
Chromosomes (paired chromatids)
Spindle
Centriole
Metaphase
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Metaphase chromosomes line up across the center
of the cell, each chromosome is connected to a
spindle fiber at its centromere
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Prophase chromatin condenses into chromosomes,
centrioles separate, spindle forms, nuclear
envelope breaks down.
Interphase cell grows and replicates its DNA
and centrioles.
Interphase
Spindle forming
Prophase
Centrioles
Centromere
Centriole
Chromatin
Nuclear envelope
Chromosomes (paired chromatids)
Spindle
Centriole
Individual chromosomes
Metaphase
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Anaphase sister chromatids separate into
individual chromosomes and move apart
Metaphase chromosomes line up across the center
of the cell, each chromosome is connected to a
spindle fiber at its centromere
Anaphase
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Prophase chromatin condenses into chromosomes,
centrioles separate, spindle forms, nuclear
envelope breaks down.
Interphase cell grows and replicates its DNA
and centrioles.
Interphase
Spindle forming
Prophase
Centrioles
Centromere
Centriole
Chromatin
Nuclear envelope
Chromosomes (paired chromatids)
Spindle
Centriole
Telophase
Individual chromosomes
Metaphase
Nuclear envelope reforming
Anaphase sister chromatids separate into
individual chromosomes and are moved apart
Anaphase
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Interphase cell grows and replicates its DNA
and centrioles.
Prophase chromatin condenses into chromosomes,
centrioles separate, spindle forms, nuclear
envelope breaks down.
Interphase
Spindle forming
Prophase
Centrioles
Centromere
Centriole
Chromatin
Nuclear envelope
Chromosomes (paired chromatids)
Spindle
Cytokinesis
Centriole
Telophase
Individual chromosomes
Metaphase
Nuclear envelope reforming
Anaphase sister chromatids separate into
individual chromosomes and are moved apart
Anaphase
Telophase chromosomes gather at opposite ends
of the cell and lose their distinct shapes- 2 new
nuclear envelopes form
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Prophase chromatin condenses into chromosomes,
centrioles separate, spindle forms, nuclear
envelope breaks down.
Interphase cell grows and replicates its DNA
and centrioles.
Cytokinesis cytoplasm pinches in half, each
daughter cell has an identical set of duplicate
chromosomes
Interphase
Prophase
Ithen PMAT
Cytokinesis
Metaphase
Metaphase chromosomes line up across the center
of the cell, and each is connected to a spindle
fiber at its centromere
Telophase chromosomes gather at opposite ends
of the cell and lose their distinct shapes- 2 new
nuclear envelopes form
Telophase
Anaphase
Anaphase sister chromatids separate into
individual chromosomes and are moved apart
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Prophase
Interphase
Metaphase
Cytokinesis
Anaphase
Telophase
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Cell Cycle Tree Map
Cell Cycleincludes..
Mitosisis divided into
Interphaseis divided into
G1 phase
S phase
G2 phase
Telophase
Prophase
Metaphase
Anaphase
And thenCytokinesis
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Draw the cell cycle diagram on pg. Label the
parts. List the stages of the cell cycle,
describe what happens in each stage (G1, G2, S
and M)
Title The Cell Cycle and Mitosis
Your Name ex. by Fred Cooks
1st The Cell Cycle Interphase
Prophase. Draw a cell in prophase using pg. 246
as a reference. List 3 facts describing events
in Prophase.
P
2nd Mitosis - Prophase
M
3rd Mitosis - Metaphase
Metaphase. Draw a cell in metaphase, and list 3
facts describing events in this phase.
A
4th Mitosis - Anaphase
T
5th Mitosis - Telophase
Anaphase and Telophase. Draw a cell in anaphase
and telophase, and list 3 facts describing events
in each phase.
6th Cytokinesis
Include these definitions
Cytokinesis. Draw a cell in cytokinesis and
define what happens to the cell.
Chromosome Centromere Centriole Spindle Sister
chromatids
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Regulation of the Cell Cycle
Section 10-3
Box 25

• For very obvious reasons, the cell cycle is a
  tightly, highly controlled process.
• Do you know why?
• Uncontrolled cell growth is cancer!!! Cancer
  can be deadly!
• Not all cells need to divide all the time, or at
  all.
• There is a time and place for cell division, and
  controlling the cell cycle is important because
  it is part of homeostasis- keeping an organism
  alive and healthy.

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Controls on Cell Division
These experiments show that controls on cell
growth and division can be turned on and off.
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What happens in your body?

• Similar processes happen in your own body.
• What if you get a cut on your finger? A broken
  bone?
• When youre injured, cells at the edge of the cut
  or break are stimulated to divide rapidly and
  produce new cells, starting the process of
  healing.
• When the gap is repaired, the controls for cell
  division turn off again, and everything returns
  to normal.

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Cell Cycle Regulators

• Tim Hunt and Mark Kirschner found a protein that,
  when injected into non-dividing cells, would
  cause mitotic spindle fibers to form.
• Levels of this protein rose and fell, depending
  on the phases of the cell cycle produced when
  needed for division, not produced when no cell
  division is occurring.
• They called the protein Cyclin (for cycle)
• Cyclins regulate the timing of the Cell Cycle
  in Eukaryote cells (your cells!)

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Hunt and Kirschners Experiment
A sample of cytoplasm is removed from a cell in
mitosis.
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The reason for this effect is the protein Cyclin,
which triggers cell division in non-dividing
cells.
The sample is injected into a second cell in G2
of interphase.
As a result, the second cell enters mitosis.
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Internal and External Regulators
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• Internal regulators regulating proteins that
  respond to events inside the cell, and control
  the cell cycle allow cell cycle to proceed only
  when certain process have happened inside the
  cell.
• Similar to You cant eat your dessert until you
  clean your plate!
• External regulators regulating proteins that
  respond to events outside the cell, and control
  the cell cycle

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Uncontrolled Cell Growth

• Cancer.
• Such a scary word, isnt it?
• Most common cancers
• Men Prostate cancer (33)
• Lung (13)
• Women Breast (32)
• Lung (13)

Affects 1 in 6 men
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Affects 1 in 13 men
Affects 1 in 7 women
Affects 1 in 17 women
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Pretty frightening, yes?
American Cancer Society 2004 Statistics
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Cancer

• Cancer cells do not respond to the signals that
  regulate growth of most cells.
• They divide uncontrollably and form masses of
  cells called Tumors that can damage the
  surrounding tissues.

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Cancer

• Cancer is a disease of the Cell Cycle.
• To find a cure for this horrible disease, we must
  first deeply and completely understand the Cell
  Cycle, what regulates it, and how it can go
  wrong, resulting in cancer.
• This is a major scientific challenge, but at
  least we know now where to start searching for a
  cure- the Cell Cycle.

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Stem Cells

• When you were first conceived, you started out as
  a SINGLE cell. One cell.
• That one cell then divided over and over,
  (Mitosis) producing cells that could and would
  become all the specialized parts of your body.
• Fetal Stem Cells the cells in the earliest
  stages of fetal (baby) development, they can
  potentially become any cell type in the body.
• Adult Stem Cells usually found in the bone
  marrow, can be induced (pushed) to become other
  cell types like muscle, nerve and liver cells

Controversial Unethical?
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Has the promise to repair many injuries and
replace damaged organs (ex. liver)
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Meiosis
Section 11-4
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• Humans have 46 chromosomes in every cell of our
  bodies except the sex cells or gametes (eggs and
  sperm)- they have 23 chromosomes
• When a baby is conceived, an egg from mom and a
  sperm from dad, combine into the first cell of
  the new baby. 2323 46

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46
What would happen if the egg and sperm both had
46 chromosomes?
Baby would have 92 chromosomes!! Disaster!
92 chromosomes
death, disease
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Remembering Meiosis
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• Mitosis is a process that occurs in almost every
  cell of your body (body cells), except the sex
  cells, or gametes.
• Mitosis My toe sis, it happens in your toes!
• Meiosis is a process of cell division that
  doesnt happen in your toes, it only happens in
  your sex cells, gametes
• Meiosis My OH! Sis (as in uh-oh!)

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Meiosis

• To solve this problem, the cells in the gametes
  (eggs and sperm), undergo Meiosis instead of
  Mitosis, when they divide.
• Why Meiosis?
• Most cells in our body are Diploid (di 2)
• Diploid have 2 sets of chromosomes, 2n (one
  from mom, one from dad)
• Sex cells, or gametes, are Haploid
• Haploid have 1 set of chromosomes, 1n

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Chromosome Number

• An example.
• Fruit Flies (Drosophila), have 8 chromosomes
  total 4 from dad fruit fly, 4 from mom fruit
  fly.

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2n 8
Diploid number?
Haploid number?
1n 4
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Phases of Meiosis
Homologous same chromosome, it just comes from
different parents (mom or dad)

• How are haploid (1n) gamete cells produced from
  diploid (2n) cells?
• By Meiosis (my-OH-sis)
• Meiosis process of reduction cell division
  where the of chromosomes per cell is cut in ½
  by the separation of homologous chromosomes

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• Meiosis involves 2 distinct divisions,
• Meiosis I
• Meiosis II
• Results of Meiosis? cells with a haploid (1n)
  number of chromosomes

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Meiosis I
Interphase I
Prophase I
Chromosome duplication
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During prophase I of Meiosis, when the tetrads
form, a phenomenon called Crossing Over can
occur.
You got chocolate in my peanut butter!
You got peanut butter in my chocolate!
Sorry!
Hey hot stuff, wanna dance?
Owww! My arm!
Who me?
I think he likes me!
Help!
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Meiosis I
Interphase I
Prophase I
Metaphase I
Anaphase I
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Meiosis I
Interphase I
Prophase I
Metaphase I
Anaphase I
Telophase and Cytokinesis
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Meiosis II
The 2 new cells now enter a 2nd round of meiotic
division
No more chromosome duplication
prophase II
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Meiosis II
prophase II
metaphase II
Prophase II of meiosis I results in 2 haploid
daughter cells, each with ½ the of chromosomes
as the original cell
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Meiosis II
4
3
anaphase II
telophase II
prophase II
metaphase II
2
1
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Flow Chart for Meiosis
I
P
Interphase I
M
Prophase I
A
Metaphase I
Anaphase I
T
92
Telophase I Cytokinesis
92
92
92
Humans 2n 46
46
P
Prophase II
M
A
T
Telophase II Cytokinesis
Anaphase II
Metaphase II
46
46
46
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4 daughter cells with haploid (1n)
I then PMAT..PMAT
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Gamete Formation

• Why do we even have Meiosis?
• To make gametes (eggs and sperm).
• Male gametes sperm
• Female gametes eggs

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Why do we need eggs and sperm?
End of Chapter 10 and Chapter 11 Section 11-4