Download Cell Division and Reproduction

What is going on?
Activating Strategy: Check out this video
• Teacher Tube Bacterial Growth - YouTube
Cell Division and
Reproduction
EQ: Why do cells need to divide and
reproduce
Why would a cell need to divide?
• GQ- Can a cell just keep getting bigger and
bigger?
Think about it:
Mr. Whitaker’s classroom supply rule
• Has your body changed in the past six months?
How did you recognize this change?
• Has anyone broken a bone or required stitches?
How does your body repair itself?
• Cells have to make more of themselves to
repair wounds, heal bones, replace worn out
cells, and to allow an organism to grow in size.
What is cell division?
Cell Division- is the process by which a cell
divides into 2 new daughter cells
• Solves the problem of information
overload on cell resources
• Increases the surface area to volume ratio
so that diffusion can efficiently reach the
interior of the cell.
What is reproduction?
The Cell theory says that all cells
come from pre-existing cells.
Reproductionthe formation of new individuals
from existing individuals.
• One of the most important
characteristics of living things.
• There are two types of
reproduction:
• Asexual reproduction
• Sexual reproduction
EQ: What is asexual reproduction?
Asexual reproduction –
Production of new
organisms from a single
parent cell or organism.
• Does not involve the
fusion of nuclei
• New organisms are
identical to the parent.
• Involves both cell division
and the replication of the
genetic material
Parent cell
2 identical daughter cells
Examples of Asexual reproduction
Some plants can
produce
plantlets along
leaves or stems
Bacteria cells
reproduce in a
process called
binary fission.
Animals:
Eventually the
bud will separate
from the parent
Hydra forming a
new individual
identical to the
first one.
EQ: What is the Cell Cycle?
Cell Cycle: Is the series of
events that cells go
through as they grow and
divide. There are 4
stages:
• G1- cells grow
• S- DNA replicates
• G2- organelles double
• M- mitosis and
cytokinesis
The cell cycle is a
continuous process
What are Chromosomes
Chromosomes are bundles of
Genetic information known
as DNA
• The chromosome is made
up of super condensed
chromatin: a complex of
DNA and histones (a
protein)
• The coiling of chromatin into
a chromosome allows for
the equal division of the
DNA during cell division
Chromosome structure
• Chromatid- one of the
two copies of the
genetic material of a
cell.
• Centromereattachment site for the
sister chromatids.
Holds them together.
chromatid
Chromosome with
two sister chromatids
Human Karyotype
Cell before it
enters the Sphase of the cell
cycle
Often called the
Resting phase
3 phases of cell cycle
are in interphase
What happens
•Cell grows in size- G1
•DNA replicates - S
•Organelles double in
number- G2
GQ: Why is it important for the DNA to
replicate before the cell divides?
• So that each new daughter cell will have a
complete copy of the DNA
Parent cell
2 identical daughter cells
Vocabulary closure
• Select 2 words from this list.
• Make up a definition for these words and
write the definition only on the index card.
Chromatid
Chromosome
Centromere
Reproduction
Cell division
Asexual reproduction
Chromatin
Cell cycle
the cell cycle
Often called the
Resting phase
3 phases of cell cycle
are in interphase
What happens
•Cell grows in size- G1
•DNA replicates - S
•Organelles double in
number- G2
EQ: What is Mitosis:
Mitosis is:
• An orderly series of changes in the
nucleus
• Comes after the exact duplication of the
complete set of chromosomes in a cell
• Involves the equal separation of these
chromosomes into two new nuclei
• Each nuclei gets a complete set of
chromosomes
4 Stages of Mitosis:
What happens
•DNA forms
chromosomes(Chromosomes Condenses
or coils)
•Spindle forms
•Centrioles move
toward opposite
poles
•Nuclear membrane
starts to disappears
What happens
•Nucleus has
disappeared
completely
•Chromosomes line up
in the middle of the
cell “equator”
What happens
•Chromosomes are
pulled apart at the
centromere by the
spindle fibers
•The separated
Chromatids move
to opposite poles
What happens
•Nuclear membrane
forms around each
group of
chromosomes
•Chromosomes
uncoil
•Cytokinesis begins
by the pinching in of
the plasma
membrane
Cytokinesis is:
• the separation of the cytoplasm to divide
the two new nuclei into separate cells. It
starts towards the end of Telophase.
• It results in the formation of 2 cells.
Plant cell: cell
plate formation
Animal Cell: Cleavage
furrow
animal cell vs. plant cell
While both animal and plant cells have similar cell
cycles and proceed through the same stages of
mitosis, there are two significant difference:
1). In cytokinesis:
• In animal cells, the plasma membrane pinches in
forming a cleavage furrow which form two new
cells.
• In plant cells, a cell plate forms between the cells.
2). Plant cells do not have centrioles to attach to the
spindle fibers.
End result of mitosis
1. Two daughter cells are formed
2. Each daughter cell contains the exact
kind and number of chromosomes form
the parent cell.
Animations and Videos of
Mitosis
• http://www.cellsalive.com/mitosis.htm
• http://evanblum.com/school/mitosis.swf
• Mitosis (Somatic Cell Division) - YouTube
EQ: What is sexual reproduction
• Sexual Reproduction:
The production of a new
organism that involves two
parent organisms
• Each parent contributes
1/2 of the genetic material
for the new individual.
• Involves the fusion of
nuclei
• New individual is NOT
identical to either parent
Specialized cells
from each parent
Cell Division in Sexual
Reproduction
Diploid: 2N
means that a cell has two sets of chromosomes. Humans
have 23 pairs of chromosomes. The diploid number is
46.
Haploid:1N
means that a cell has only a single set of chromosomes.
Gametes are cells that are haploid
Gametogenesis:
• process in which gametes are produced
• Occurs in the gonads (ovaries, testes)
• Results in cells that are haploid.
* When gametes (1N) combine a diploid (2N) zygote is
formed
EQ: What is Meiosis?
Meiosis:
type of cell division where number of
chromosomes are cut in half.
Produces 4 haploid cells from one diploid
cell.
There are two distinct divisions in Meiosis.
• Meoisis I
• Meosis II
Process of Meiosis I
Meiosis I:
Consists of Interphase, Prophase I,
Metaphase I, Anaphase I, and Telophase I.
The phases in Meiosis I are similar to those in
Mitosis except for a few things:
a). In Prophase 1: Synapsis occurs.
This is when the matching (homologous)
chromosomes join to form a tetrad.
What is the importance of Synapsis and tetrad
formation?
• Tetrads contain 4 sister
chromatids called
homologous pairs
• Allows for exchange of
segments between the
chromatids by a process
called Crossing Over.
• Crossing over increases
genetic variability.
Process of Meiosis I
b). Metaphase I:
Tetrads line up at the equator
c). Anaphase I:
• Tetrads separate from each other and
move to the poles of the cell.
• Occasionally the tetrads do not separate
correctly. This is called nondisjunction.
Importance of Nondisjunction
• Nondisjunction results in an
unequal division of the
chromosomes.
Why might this be a problem?
Some gametes will have too
many chromosomes, others
will not have enough.
*Can be a source of disease
and syndromes. People with
Downs syndrome have an
extra chromosome (trisomy
21)
Process of Meiosis I
d). Telophase I- Nuclear membrane reforms around
chromosomes
e). Cytokinesis takes place forming two new cells.
• note: cross this line off in your notes.
• However, the genetic material is not like the parent
cell.
Process of Meiosis II
• The cells produced in the first division now enter a
second round of division known as
Meiosis II.
• NO Chromosome Replication takes place
between the end of Meiosis I and the start of
Meiosis II.
• The phases are similar to mitosis and Meiosis I
and are called prophase II, metaphase II,
anaphase II, and telophase II.
Result of Meiosis
• Formation of 4 daughter cells
• Each daughter cell is haploid: contains only 1 set
of chromosomes
Video of Meiosis
http://www.youtube.com/watch?v=6xM
XKU7JnMQ&feature=related
Meiosis in sexual reproduction
• Spermatogenesis:
1. in testes, males produce sperm
2. Each sperm contains 23 chromosomes
3. Each sperm is motile
• Oogenesis:
1. In ovaries, eggs (ova) are produced
2. 4 cells are produced, only one becomes an
egg
3. The three remaining ones are small and
degenerate. They are called polar bodies.
Karyotype of a gamete produced by meiosis
Haploid gamete cell
Diploid body cell karyotype
Comparison of Mitosis and Meiosis
Mitosis
Associated with asexual
reproduction
Meiosis
Associated with sexual
reproduction
Daughter cells are identical
to parent cells
Daughter cells have half the
# of chromosomes as parent.
Cells are smaller due to no
growth between divisions.
Involves 1 cell division
Involves 2 cell divisions
No exchange (crossing over) Exchange (crossing over)
between homologous
between homologous
chromosomes
chromosomes
From One Cell to Many
THINK ABOUT IT
• The human body contains over a 100 Trillion
cells all of which came from a single cell, the
fertilized egg called the zygote
• There are hundreds of different cell types that
perform different functions.
ex: liver cells, red blood cells, nerve cells
http://www.teachersdomain.org/resource/tdc
02.sci.life.cell.stemcellvid/
How do the cells get to be so different
from each other?
• The process by which cells become specialized
is known as differentiation.
• Differentiation is controlled by genes, the genetic
instructions encoded in the DNA of every cell.
• Genes instruct each cell how and when to build
the proteins that allow it to create the structures,
and perform the functions, specific to its type of
cells
Stem Cells
• Embryonic Stem Cells
• Researchers have grown stem cells isolated
from human embryos in culture.
• Their experiments confirmed that embryonic
stem cells have the capacity to produce most cell
types in the human body.
Stem Cells
Adult Stem Cells
•Adult organisms contain some types of stem
cells.
•They can produce many types of differentiated
cells.
•Adult stem cells of a given organ or tissue
typically produce only the types of cells that are
unique to that tissue.
Cell cycle regulation
• There are regulatory proteins that control
the cell cycle so that cells do not grow and
divide continually when new cells are not
needed
These proteins are called cyclins
• The genes that produce regulatory
proteins can be turned on and off like a
switch. Ex: p53, Mad1
What happens when the controls
fail?
When the controls of the cell cycle fail, cell
growth and division goes unchecked.
Cell Cycle - YouTube
• Cancer is a disorder in which body cells
lose the ability to control cell growth.
• Cancer cells divide uncontrollably to form
a mass of cells called a tumor.
What Causes Cancer?
• Cancers are caused by defects in genes that
regulate cell growth and division.
Tumor suppressor and oncogenes YouTube
• Some sources of gene defects are smoking
tobacco, radiation exposure, defective
genes, and viral infection.
• A damaged or defective p53 gene is common in
cancer cells. It causes cells to lose the
information needed to respond to growth
signals.
What is this?
Can you describe
what is happening
in:
G1:
Cells grow
S:
Chromosomes
replicate or
synthesize
(why is this phase so
important during
cellular division?)
Cell Cycle
G2:
Cells grow and
organelles double
What cell division is used in asexual
reproduction?
Mitosis
Describe the offspring that result
from asexual reproduction
They are identical to the parent
organism. They have the exact same
number of chromosomes.
What is happening in each phase
of Mitosis?
***Interphase is
a part of cell
cycle, but not a
part of mitosis
What cell division is used in sexual
reproduction?
Meiosis
Why is meiosis necessary for
sexual reproduction?
Gametes must be haploid. If not, the
organism would end up with too many
chromosomes.
What is this structure called?
Tetrad
What is the process called that forms this
structure?
synapsis
When in Meiosis does it occur?
prophase I
Homologous pairs. One chromosome is from the
father, the other matching one in the set is from
the mother
1. Synapsis allows for crossing over.
When chromosomes
synapse, what can happen
between the homologous
chromosomes? Is this a
good thing?
2. This recombination increases the genetic
variability of the population.
3. This is usually a good thing as it can help a
population to survive in a changing environment.
Know what happens in Meiosis 1
and in Meiosis 2
Production
of gametes
gonads
two
No change
Cut in half.
Daughter cells are
diploid
Gametes are
haploid
eight
two
Exactly the
same