-This week we are talking about how cells reproduce…
Next week we will talk about how organisms reproduce…
Why Do Cells Need to Reproduce?
-Growth, Repair, Replacement
Cells divide whenever a tissue / organ / organism is growing
or needs repair.
-What is the result of cell reproduction?
A cell divides into two cells by making a copy of itself.
The result is two genetically identical cells.
-Cell Division = Cell Reproduction (this can be confusing!)
Mitosis
Mitosis is part of a cell’s life cycle.
Cell division occurs during the stage of
Mitosis.
During this stage, new cells with
identical genetic information are
formed.
The genetic material and cytoplasm are
equally divided between two cells.
What is the genetic material?
à
Chromosomes are
structures located in the
nucleus of the cell.
Chromosomes are made of
DNA and protein.
Chromosomes contain
genes.
Genes control the
physical
characteristics of a
species.
All the genes of an
organism make up
the organism’s
genome.
All organisms of
the
same species
contain the
same number of
chromosomes
in their nuclei.
The
Cell
Cycle
All cells develop from
existing cells.
This enables multicellular
organisms to grow, replace
dead cells, and reproduce.
A cell’s life can be
described with the cell
cycle.
There are three
stages of the cell cycle:
–  Interphase
–  Cell Division (mitosis
or meiosis)
–  Cytokinesis
Interphase (occurs before mitosis begins)
Three Parts of Interphase:
G1 phase: The cell is growing and performing its day to day functions.
S phase: The cell replicates its DNA.
G2 phase: The cell is preparing for cell division.
Main Point of Interphase:
DNA (chromosomes) are copied (# doubles)
BEFORE Interphase
AFTER Interphase
What Interphase looks like under the microscope:
Distinct nucleus. You should be able to easily distinguish the
nucleus from the cytoplasm.
Chromatin DNA. Chromosomes are yet fully condensed, this is
called chromatin. Because chromatin is very thin, you can not
see individual DNA strands. There are indistinct swirls of
chromatin dispersed throughout the nucleus.
Cell Cycle Poster
1.  Count the number
of cells in each
phase and write
this on your
poster.
Interphase =
Prophase =
Metaphase =
Anaphase =
Total = 73
2. Calculate the
percentage of time
the cells are in each
phase. Create a pie
chart representing
your data and
answer the analysis
questions.
THE CELL CYCLE
Interphase
Notes
-During
Interphase the
DNA replicates.
-This organism’s
body cell has 4
chromosomes at
the beginning of
Interphase.
-Before prophase,
there will be 8
chromosomes.
What Interphase looks like under the microscope:
Distinct nucleus. You should be able to easily distinguish the
nucleus from the cytoplasm.
Chromatin DNA. Chromosomes are yet fully condensed, this is
called chromatin. Because chromatin is very thin, you can not
see individual DNA strands. There are indistinct swirls of
chromatin dispersed throughout the nucleus.
THE CELL CYCLE
Prophase
Notes
-The
chromosomes
form pairs during
prophase.
-The nuclear
membrane begins
to break down.
This organism’s body cell had 4 chromosomes at
the beginning of Interphase.
After DNA replication, the cell has 8
chromosomes (as shown above) and the cell
enters prophase.
Prophase
THE CELL CYCLE
Metaphase
Notes
-The nuclear
membrane has
completely
disappeared.
-The paired
chromosomes
line up in the
middle.
-Centrioles
release spindle
fibers.
Metaphase
THE CELL CYCLE
Anaphase
Notes
The centrioles
pull the spindle
fibers back,
which result in
the
chromosomes
being pulled
apart to
opposite sides.
Anaphase
THE CELL CYCLE
Telophase
Notes
A nuclear
membrane
forms around
each set of the
separated
chromosomes
(chromatin).
Telophase
Cytokinesis
(the stage after mitosis)
Notes
-The cell
membrane forms
around each of
the two cells.
-The resulting
cells are identical
to the original
parent cell.
After mitosis, there are 2 cells with 4
chromosomes (chromatin) in each cell.
Cytokinesis
Cell Cycle
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
Cell Cycle
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
What is the result of Mitosis?
two identical cells each with
the same number of
chromosomes
Videos:
Mitosis
Cell Reproduction