Download Mitosis and Cellular Reproduction

Cellular Reproduction &
Mitosis
Biology
Rainier Junior/Senior High School
Mr. Taylor
Cellular Reproduction
Remember that ORGANISMS reproduce to:
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produce new individual organisms
prevent extinction
CELLS reproduce to:
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continue the existence of an organism through
growth and repair
form gametes (sex cells: sperm (♂) and
ovum/egg (♀)
Cellular Reproduction
Growth: Cells must maintain a favorable
surface area : volume ratio. If they are too
large, they can’t get enough nutrients or
get rid of waste products quickly enough.
Repair:
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Cells can become damaged or worn out.
Some live short lives and need to be
replaced often (skin, blood cells, digestive
tract cells)
Cellular Reproduction
Growth: Cells must maintain a favorable
surface area : volume ratio. If they are too
large, they can’t get enough nutrients or
get rid of waste products quickly enough.
Repair:

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Cells can become damaged or worn out.
Some live long lives and are seldom if ever
replaced (brain, spinal cord, and other nerve
cells)
Reproductive Methods
By convention:

Parent cells produce daughter cells.
This has nothing to do with gender! It’s just how
biologists have chosen to name the original cell
and the two cells that are created.
Reproductive Methods
Two styles of reproduction
 Asexual:
One parent, daughter cells are exact
genetic replicas of the parent cell. We say
that the offspring are exactly like the
parents.
There are at least 5 different kinds of
asexual reproduction.
 Sexual:
usually requires two parents, daughter
cells are a blending of traits of the parents.
We say that the offspring are similar to the
parents.
Asexual Reproduction
1. Binary Fission: The cell simply splits into
two equal-sized cells after the
chromosomes have replicated.

(Most cells do this.)
2. Budding: A small cell ‘buds’ off the larger
parent cell. The small daughter cell will
grow in size to equal the original parent
cell.

(Yeast cells do this.)
Asexual Reproduction
3. Spores: Small reproductive cells that are
formed with a tough outer covering and
very little cytoplasm.
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These are resistant to heat, cold, dryness, or
other harsh conditions.
They will begin to grow again when the
conditions are good for growth.
(Anthrax uses this method of reproduction.)
Asexual Reproduction
4. Vegetative propagation: “Runners”
originally attached to a parent plant can
become separate plants.

Strawberries, grass, hens & chicks (a plant)
do this.
5. Regeneration/fragmentation: Regrowth of
body parts lost for a variety of reasons.

Most sea stars can regenerate arms and
SOME lizards can regrow lost tails.
Sexual Reproduction
Two specialized sex cells – called
gametes – unite in the process of
fertilization to form a zygote.

There are only two kinds of gametes:
Sperm: the male gamete
Ovum or egg: the female gamete. (Ovum is
singular, ova is plural)
The zygote will mature into an embryo.
Mitosis
Chromosome: A strand of DNA and
structural proteins containing numerous
genes.
Gene: A portion of a DNA molecule that
codes for a single protein or RNA molecule.
Mitosis
Homologous chromosomes: Two chromosomes
that are the same length and shape, and contain
genes for the same traits in the same locations.
One comes from the father, one comes from the
mother.
 Diploid: For each type of chromosome, one
chromosome from each parent is present.
 Haploid: For each type of chromosome, only
one parent’s chromosome is present.
Mitosis
Autosomal chromosomes: Have nothing
to do with gender determination.
Sex chromosomes: Only one pair in each
cell. These do determine gender.

Two forms, X and Y
XX = female
XY = male
Mitosis
Karyotype: A picture of the cell is taken
while it is dividing and used to make a
chromosome map of that cell.
Sex cells: gametes (as noted before)
Somatic cells: “normal” body cells, any cell
that is not a gamete.
Mitosis & the Cell Cycle
Each somatic cell undergoes a similar life process
called the Cell Cycle.
We start with the G1 (Gap1), or First growth
phase.
 The cell is just being a cell. It is creating
movement if it is a muscle cell, it is making
enzymes if it is a pancreatic cell, it is carrying
on photosynthesis if it is a leaf cell.
Mitosis & the Cell Cycle
Each somatic cell undergoes a similar life process
called the Cell Cycle.
Next comes the S phase, or DNA synthesis
phase.
 The cell’s DNA replicates, that is, it makes
copies of itself.
 The copies, now called chromatids, are
attached together by a centromere.
Mitosis & the Cell Cycle
Each somatic cell undergoes a similar life process
called the Cell Cycle.
Now comes the G2 (Gap 2) phase, or second
growth phase.
 The cell prepares to divide by making more of
each type of organelle and assembling microtubules into short strands.
Mitosis & the Cell Cycle
Each somatic cell undergoes a similar life process
called the Cell Cycle.
The G1, S, and G2 phases are collectively called
INTERPHASE.
 The cell spends most of its life in interphase.
 Some cells, such as muscle cells and nerve
cells, remain in interphase all of their lives. If
they die, they can’t be replaced.
Mitosis & the Cell Cycle
Each somatic cell undergoes a similar life process
called the Cell Cycle.
After G2, the cell enters into Mitosis (division of
the nucleus) and Cytokinesis (division of the
cytoplasm).
When mitosis and cytokinesis are complete, the
cell returns to the G1 phase and the cycle
continues.
Mitosis
1.
2.
3.
4.
Mitosis, the division of the nucleus, is
broken down into 4 phases.
Prophase
Metaphase
Anaphase
Telophase
Mitosis: Prophase
Mitosis, the division of the nucleus, is
broken down into 4 phases.
 In prophase the chromatids coil up and
become visible as separate structures.
 The nuclear membrane breaks down and
the nucleus disappears.
 The spindle forms.
 The centromeres attach to a spindle fiber
Mitosis: Metaphase
Mitosis, the division of the nucleus, is
broken down into 4 phases.
 In metaphase the chromatids align along
the equator (the MIDDLE) of the cell.
Mitosis: Anaphase
Mitosis, the division of the nucleus, is
broken down into 4 phases.
 In Anaphase the centromeres divide and
the chromatids (now called
chromosomes again) are pulled to
opposite ends (the poles) of the cell by
the spindle fibers.
Mitosis: Telophase
Mitosis, the division of the nucleus, is
broken down into 4 phases.
 Telophase is the opposite of Prophase;
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The nuclear membrane reforms
The chromosomes uncoil and are no longer
visible as separate things (they look like
tangled spaghetti)
The spindle breaks down
Mitosis: Cytokinesis
Our textbook separates cytokinesis from
mitosis, others include it with telophase.
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Cytokinesis is the division of the cytoplasm
and organelles and it occurs almost
simultaneously with telophase.
In animal cells, a belt of proteins pinches the
cell membrane and divides the cell in two.
In plant cells, a cell plate begins to form
between the two nuclei. It will eventually
mature into the cell wall.
Mitosis
Mitosis