Download Cell Cycle and Mitosis

Cell Cycle and Mitosis
BILL
• Why do cells divide? (4 marks)
• Divide as organisms grow to keep SA:V ratio
high (more efficient cell)
• Cell division allows for cell differentiation
• Cells divide during embryonic development
• Cells divide to replace dead, damaged, or
infected cells
• Cell division used in asexual reproduction
Cell Cycle
• Cell cycle is the process that describes
how cells grow and divide.
• The end of the cell cycle results in two
new identical cells (in most cases). These
cells are called daughter cells.
• http://highered.mcgrawhill.com/sites/0072495855/student_view0/
chapter2/animation__how_the_cell_cycle_
works.html
Interphase
• Largest part of cell cycle
(90%) is occupied by the
INTERPHASE.
• Cells metabolic activity is
very high during
interphase.
• This phase includes G1,
S, and G2 phases.
G1
• G1 – Major portion of
cell growth occurs
during this state.
• Production of
proteins &
organelles
• G stands for “Gap”.
Synthesis (S) Phase
• “S” Stands for
synthesis of DNA.
• DNA is replicated
during S phase (seen
as the duplication of
chromosomes).
• Cells begin S phase
with a single copy of
each chromosome
and finish with two
identical copies of
each chromosome.
G2 Phase
• Cell enters second growth
phase. (Gap 2)
• Cell prepares to enter the
Mitotic phase.
• Chromatin begins to
condense into
chromosomes
• Cell completes
preparations for cell
division. (production of
necessary organelles)
Mitotic Phase (M phase)
• Part of the cycle when the cell
actually divides (about 10% of
life cycle)
• Divided into two stages:
• Mitosis – nucleus and its
contents divide and are evenly
distributed to form two
identical daughter nuclei. (4
stages: prophase, metaphase,
anaphase, telophase)
• Cytokinesis – cytoplasm
divides in two and the cell
finishes dividing.
BILL
• What is the cell cycle? What is the result
of the cell cycle?
• Process that describes how a cell grows
and divides.
• At the end of the cell cycle, there are two
identical daughter cells.
Cell Cycle Review
• Label and Annotate the diagram of the cell
cycle on your note sheet.
Anatomy of a chromosome
Key Terms:
• The following are key terms relating to the
overall structure of chromatin in the S-phase of
mitosis:
– Chromatin – The combination of DNA and proteins
(called histones) that constitutes chromosomes.
– Chromosome – tightly packaged molecules of
condensed chromatin. Gene carrying structure
found in the nucleus of a eukaryotic cell. Most
visible during mitosis of eukaryotic cell.
– Sister Chromatid – one of the two identical parts of
a duplicated chromosome in a eukaryotic cell.
(formed after s phase of cell cycle)
– Centromere – region of chromosome where two
sister chromatids are joined and where spindle
microtubules attach during mitosis.
Cell Division
• http://highered.mcgrawhill.com/sites/0072495855/student_view0/
chapter2/animation__mitosis_and_cytokin
esis.html
• http://www.youtube.com/watch?v=DD3IQk
nCEdc
Organelles we have NOT
discussed that are used in Mitosis
• Microtubules – Fibers that make up the
cytoskeleton of a eukaryotic cell. Composed
primarily of the protein actin. Attach to and
separate chromosomes during mitosis
• Centrosome – Organelle in the cytoplasm that
makes and controls microtubules. Also called
the microtubule-organizing center (MTOC).
• Together, these organelles control the
movement and separation of chromosomes
during mitosis
MITOSIS
• After all preparations have been made by
the cell, the final stage of the cell cycle is
MITOSIS. Mitosis is subdivided into 4
main phases:
– Prophase
– Metaphase
– Anaphase
– Telophase
– Cytokinesis (technically a separate part)
Bill
• Summarize the steps of mitosis/cytokinesis.
• Prophase – chromatin condenses into chromosomes, the nuclear
membrane breaks down, and the centrosomes move towards
opposite sides of the cell.
• Metaphase – chromosomes line up at the equator of the cell, with
sister chromatids facing opposite sides of the cell.
• Anaphase – sister chromatids are pulled towards opposite sides of
the cell. At the end of this phase, each side will have an identical set
of chromosomes.
• Telophase – chromosomes are on opposite sides of cell and the
nuclear membrane begins to reform around them. Chromosomes
unwind into DNA as the cell elongates and prepares for cytokinesis.
• Cytokinesis – cytoplasm pinches in and the cell will divide.
• At end of process, there are two identical daughter cells.
Prophase
1. Chromosomes
appear in nucleus
2. Nuclear membrane
disappears.
3. Centromere of each
chromosome
attaches to
microtubules.
4. Centrosomes begin
to move toward
opposite sides of
cell.
Prophase
Metaphase
1. Chromosomes move
to equator (middle)
of cell
2. Centromeres line up
along middle of cell.
3. Sister chromatids
are facing opposite
directions of cell
4. Chromosomes can
move via
microtubules
Metaphase
Anaphase
1. Sister chromatids
now move
towards
opposite sides
of the cell.
2. Microtubules
retract.
3. At the end of
phase, each side
of cell has a
complete set of
identical
chromosomes
Anaphase
Telophase
1. Chromosomes are now
on opposite side of
cell
2. Nuclear membrane
begins to reform
around each set of
chromosomes.
3. Chromosomes unwind
into chromatin.
4. Cell is elongates and
prepares for
cytokinesis.
Telophase
Cytokinesis
• Cytokinesis is the
inward pinching of the
plasma membrane to
form cleavage
furrows.
• In other words, the
cell actually divides.
• Mitosis results in two
genetically identical
daughter cells
Cytokinesis
Mitosis/Cytokinesis
•
•
•
•
•
P – Princes (Prophase)
M – Must (Metaphase)
A – Always (Anaphase)
T – Tackle (Telophase)
C – Chumps (Cytokinesis)
• http://www.youtube.com/watch?v=DD3IQk
nCEdc
Summary
Explain how mitosis ensures that
daughter nuclei are genetically identical
• Exact copies of DNA are made during S-phase.
DNA replication includes checks to ensure accuracy.
• DNA is supercoiled (condensed into
chromosomes) to keep it all together.
• In metaphases, all sister chromatids line up at the
equator.
• When the microtubules attach to centromeres, they
are in the correct position with one
chromatid/copy facing each side of the cell
• In anaphase, the chromatids are pulled apart and
exactly the right number are pulled in opposite
directions
• There is clear separation between newly forming
nuclei in telophase to allow for cytokinesis,
ensuring no chromosomes are on the wrong side.
Summarize how mitosis
produces two genetically
identical daughter cells
• Exact copies of each chromosome are made during the
S phase of interphase by
• In prophase, DNA condenses into easily managed
chromosomes
• In metaphase, all chromosomes line up at equator of
cell, with sister chromatids facing opposite sides of the
cell
• In anaphase, exactly the right number of chromosomes
are pulled to opposite sides
• In telophase, there is a clear space between new nuclei
so that when the cell divides, no chromosomes are
caught on wrong side.
Reasons for Cell Division
Why do Cells Divide?
• SA:V ratio must be large enough for efficient
cells
• Cell division allows for growth of organisms, as
well as differentiation
• Occurs most frequently in developing embryos
• New cells constantly required to replace dead,
damaged, or infected cells
• Cell division is also used in asexual
reproduction (self-replication)
Mitosis Questions
• Answer questions on worksheet (10
minutes to finish)
TAKE HOME TEST
• Test questions are online under homework
tab
• Answer questions on answer sheet
provided
• Due Monday 3/21/16
Good Resource!
http://www.biology.arizona.edu/Cell_bio/tutor
ials/cell_cycle/main.html
Cancer video:
http://www.youtube.com/watch?v=acUl9J
C70e8
BILL
• Turn in take home test
• A chemical called colchine disrupts the formation of
microtubules. What effect would this drug have on a cell
going through mitosis?
– Chromosomes would not divide evenly, or at all necessarily.
Microtubules attach to chromosomes and direct their movement,
so without that organelle, the chromosomes would not move.
• If a parent cell has 24 chromosomes, how many
chromatids would be present during metaphase of
mitosis?
– 48 sister chromatids
• Explain where cytokinesis occurs in the cell cycle.
– Immediately after mitosis and before the two new daughter cells
enter interphase.
CANCER
• Cancer is uncontrolled cellular
mitotic divisions, caused by
mutations in a gene that tells the
cell to stop dividing
• Typically caused by carcinogens, or
any substance, radionuclide, or
radiation that is an agent directly
involved in causing cancer
http://www.youtube.com/watch?v=LEpTTol
ebqo
Tumors
Abnormalities can sometimes occur in cells
which reproduce at a rapid rate, this in turn
may lead to the formation of tumors,
Tumors are an abnormal mass of tissue or
cells.
Tumors are the result of uncontrolled cell
division
- occurs when genetic checks that stop
cells from reproducing fail to work
- can occur in any organ or tissue,
though are most common after exposure to
carcinogens, or in more active tissue
Benign vs. Malignant Tumors
• Benign Tumors - cells stay in the same place
and the tumor stops growing before it gets
very large, so it does not spread and does not
normally harm the body.
• Malignant Tumors - cells are able to invade the
surrounding tissue and spread into nearby
organs where they can cause serious and fatal
damage.
How do cancers spread?
• Angiogenesis: tumors recruit blood vessels and
grow larger
• Metastasis: part of tumor invades the blood
vessel, travels through the blood, and starts to
form tumor in other parts of body
• http://www.youtube.com/watch?v=acUl9JC70e8
Cancer Research Project
• This project focuses on what happens when cells do not
function correctly. Many people are affected by cancer;
you may even have some family members or friends that
have or have had cancer.
• I suggest that you choose a cancer that affects someone
you know or intrigues you because it is interesting.
Cancer Research Project
• The goal is to research the cancer and orally present
information and recent research through a group
PowerPoint presentation that takes no more than 5
minutes to present.
• The presentation should be informative and include
current treatments or ways to avoid getting that cancer
(i.e., not smoking). Be creative and use color and
artwork.
• Must cite sources!!!!!!
• Be sure to reference the rubric online under homework
tab.
• Research today, tomorrow, and Wednesday. Present on
Thursday