Transcript 3.7 PPT_Mitosis

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Vocabulary Throwback…
What does it mean when you have the
PREFIX ‘A-”
Example: Abiotic?
So…
What do you think the word ASEXUAL
means?
Asexual Reproduction
HEREDITY is the process by which parent
organisms transfer their genetic
information (DNA) to offspring.
Eukaryotic organisms (plant/animal)
transfer genetic information (DNA) in the
form of CHROMOSOMES (coiled DNA).
Most human cells contain 23 pairs or 46
chromosomes.
ASEXUAL reproduction - the production of
genetically identical offspring from one
parent using MITOTIC cell division.
What does Asexual Reproduction
Result in?
Results in genetic STABILITY between
generations
This means each generation is IDENTICAL
What are the ADVANTAGES?
Advantages
No need to find a MATE (saves energy)
Rapid population growth
What are the DISAVANTAGES?
Disadvantage
No VARIATION (all identical)
Types of Asexual Reproduction
MITOSIS

MITOSIS is the process somatic cells (“body cells”) use
to divide in our body to promote growth and development
in an organism. It is ASEXUAL reproduction.
Facts about Mitosis
DNA REPLICATES (copies itself) before
division
# of divisions: 1
# of daughter cells: 2
Daughter cells are IDENTICAL
BRAINPOP!
http://www.brainpop.com/science/cellularlif
eandgenetics/asexualreproduction/
It’s The
circle of cell
life
How do cells reproduce and
grow?
The Basics…
What must be present in EVERY cell?
What must happen BEFORE a cell
divides?
WHAT IS THIS?
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Why do cells
divide?
To replace other cells that have been
damaged or worn out
To allow multicellular organisms to grow
For asexual reproduction
Because they get too big!
What is MITOSIS?
Mitosis is the process by which the
nucleus of one cell DIVIDES into two
nuclei
Therefore, each cell has the same genetic
material as the original cell
Its like “photocopying”(or CLONING) the
cell- the two daughter cells are identical
Genetic
Information
 Genetic information is contained in the DNA of
the cell
 DNA is found in the thread-like coils called
CHROMATIN when the cell is NOT dividing
 When the cell is dividing, the chromatin
condenses (packs into) chromosomes
 genes are small sections of chromosomes that
contain the information for a specific cell
function
What makes up a chromosome?
DNA wrapped around PROTEINS!
The Big
Picture
The cell cycle
Cell Cycle
The cell
spends the
most amount of
time in
interphasegrowing
Cell CycleInterphase
 During INTERPHASE
the cell is GROWING
and preparing to
reproduce
 The cell’s DNA is being
copied (replicated)
 The DNA is in the form
of loosely coiled
CHROMATIN
Cell CycleMitosis
Remember! Mitosis is the stage of the cell
cycle in which the nucleus and cell divides
Mitosis is divided into:
Prophase
Metaphase
Anaphase
Telophase
**(Cytokinesis)**
Cell Cycle
The cell
spends a very
short amount
of time in
mitosisdividing
The phases
of mitosis
Prophase
 Chromosomes are
condensed and consist of
2 sister chromatids
 The nuclear membrane
begins to break down
 Spindle fibers appear
 The CENTROMERE joins
each pair of sister
chromatids to the spindle
fiber
 MEMORY TRICK:
Pro  PRIOR (1st phase)
Metaphase
 Chromosomes line up
along the middle of
the cell
 MEMORY TRICK:
Metaphase = Middle
Let Make our OWN Chromosomes!
Anaphase
 Spindle fibers
separate sister
chromatids and pull
them apart
 Once they have
separated they are
individual
chromosomes
 MEMORY TRICK:
Anaphase = Away
Telophase
 Spindle fibers
disassemble
 Nuclear envelope
reforms
 The nuclear envelope
will become the
nuclear membrane
 MEMORY TRICK:
Telophase = Two
Cytokinesis
 The cytoplasm is divided between the two
cells
 In animal cells, cell membrane pinches off
forming two new separate cells
 In plant cells, cell membrane pinches off and
a cell wall forms
KEY FACTS ABOUT MITOSIS
What TYPE of cells?
SOMATIC cells = BODY cells (skin,
etc.)
WHEN?
BEFORE cell division
WHY?
 REPLACE worn out cells
 GROWTH of multicellular organisms
 ASEXUAL Reproduction
 Because they cells get TOO BIG and
must divide
# of DIVISIONS?
ONE (identical daughter cells)
# of DAUGHTER CELLS?
2 (identical) daughter cells
Genetic STABILITY or VARIATION?
STABILITY (means IDENTICAL)
Mitosis in
action!
BRAINPOP!
http://www.brainpop.com/science/cellularlif
eandgenetics/mitosis/
Check Point
B
A
C
D
E
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Check Point
1. Which statement is true regarding asexual reproduction as a
method of producing offspring?
a)
b)
c)
d)
limited to unicellular organisms
common among mammals
not a method used by plants
produces offspring that are genetically identical
2. Put the pictures of mitosis (bottom right) in chronological order.
3. Why do cells divide?
4. What occurs in metaphase?
B
C
A
D
E
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Human
Chromosomes