What is cancer?
CELL
DIVISION
How do we live?
MITOSIS AND MEIOSIS
FOCUS QUESTIONS FOR UNIT
• What is cancer?
• How does cancer affect the body?
• Why do we care about stem cells?
• What problem does growth cause for cells?
LIMITS OF CELL GROWTH
• The information that controls a cell’s function is stored in DNA.
• Remember surface area to volume ratio? What effect will this have on the
cell?
1. If a cell were to grow without limit an “information crisis” would occur.
1. A cell’s SA cannot increase fast enough to meet the demands of the
internal volume of the cell.
1. If this occurs the cell will be unable to bring molecules into and out of the
cell fast enough to meet the cell’s needs and it will not survive.
LIMITS OF CELL GROWTH
• Communication from the nucleus to other organelles must be fast, in order
for the cell to function.
• Molecules within a cell can only diffuse a certain distance depending on the
size of the cell.
• SA helps with the cell's absorption of molecules and expulsion of waste.
• Cristae make up the inner membrane
of the mitochondrion that help
increase SA; to increase the chemical
reactions (of ATP), for the cell. If the
cell gets too big it would not be able to
produce enough ATP for the cell to
function. This would affect transport
and other functions in the cell.
• So if cells don’t get bigger how do
organisms survive?
– CELL DIVISION
CELL DIVISION: FOCUS QUESTIONS
• Why do our cells go through cell division?
• What are the main events of the cell cycle?
• What happens during the different phases of mitosis and meiosis? Which cells do you think use
one or other?
PROKARYOTIC CELL DIVISION
• Binary Fission
1.
The cell
• 1. Copies its DNA.
• 2. Splits its identical information.
• 3. The cell then separates into two new
cells.
1.
There is no recombination (exchange) of
genetic information therefore it is a form of
asexual reproduction.
https://www.youtube.com/watch?v=DY9DNWcqxI4
http://www.britannica.com/science/binary-fission
CHROMOSOMES
• Carry the genetic information that is
passed down each generation.
• Made up of DNA and proteins.
• Each species as its own specific number of
chromosomes. We have 46 per cell.
• A chromosome consists of two identical
chromatid sisters. When the cells
divides the sister chromatids will separate
from each other.
– Held together by a centromere.
http://learn.genetics.utah.edu/content/basics/
CELL CYCLE
INTERPHASE
• A series of events that cells go through as they grow and divide. Cells spend most of their life in
interphase.
• G0: are cells that will no longer divide but are still living and functioning: for example heart cells.
• Most cells stop dividing after about 50 divisions.
• G1pase: cells grow and synthesize new proteins and organelles.
• S Phase: Chromosomes are replicated and DNA is synthesized.
• G2 Phase: organelles and molecules required for cell division are produced.
Textbook: Pg. 245
INTERPHASE
Preparation for Division: Growth, production of proteins and organelles, and
replication of chromosomes.
https://www.youtube.com/watch?v=O3_PNiLWBjY
CELL CYCLE
MITOSIS: PROPHASE
• Longest phase of mitosis
• Nuclear envelope breaks down
• Nucleolus dissolves
• Chromatin condenses
• Centrioles move to opposite sides (poles) of the cell to the
centrosomes
• These centrioles organize the spindle that helps separate
chromosomes
CELL CYCLE
MITOSIS: PROPHASE
CELL CYCLE
MITOSIS: METAPHASE
• The chromosomes line up across the
center of the cell.
• Microtubules connect to the kinetochore
protein (these form on the centromere) of
each chromosome which attach to the two
poles of the spindle.
–This will pull the sister chromatids apart.
CELL CYCLE
MITOSIS: METAPHASE
METAPHASE
CELL CYCLE
MITOSIS: ANAPHASE
• Shortest phase of mitosis
• The centromere that joins the identical sister chromatids will separate them and they are
pulled to opposite poles of the cell
• They continue to move and become individual chromosomes until they are near the poles of
the spindle
CELL CYCLE
MITOSIS: TELOPHASE
• New nuclear
envelopes form around
chromosomes
• Chromosomes uncoil
and disperse within
envelope
• A new nucleolus forms
in each cell
CELL CYCLE
MITOSIS: CYTOKINESIS
• Cytokinesis: means movement within the cell
• Division of the cytoplasm down the middle to form two new
cells
• Each cell has a nucleus and cytoplasmic organelles
• Begins during anaphase as the chromosomes separate
• Plants: a cell plate will form and gradually develops into a
separating membrane, this forms the cell wall
CELL CYCLE
MITOSIS: CYTOKINESIS
Textbook: Pg. 245
What does this
cell division cycle
do for us?
https://www.youtube.com/watch?v=gwcwSZIfKlM
MITOSIS QUIZ
DIVISION
BASED ON FUNCTION
CELL TYPE
LIFE SPAN
CELL DIVISION
WBCS
10 HRS TO A DECADE
CANNOT DIVIDE
LINING OF SMALL
INTESTINE
1-2 DAYS
CAN DIVIDE
SMOOTH MUSCLE
LONG-LIVED
CAN DIVIDE
RBCS
LESS THAN 120 DAYS
CANNOT DIVIDE
CARDIAC MUSCLE
LONG-LIVED
CANNOT DIVIDE
NEURON
LONG-LIVED
MOST DO NOT DIVIDE
SKELETAL MUSCLE
LONG-LIVED
CANNOT DIVIDE
What does this tell us about cells?
All cells have a function which varies (is differentiated) from one cell
type to another.
CELL DIFFERENTIATION AND STEM
CELLS
• Not all cells are alike: neural, skin, liver, heart, etc.
• There are many sizes, shapes, structures and internal organization. Each cell can do something
different.
• Your body can contain over 200 different types of cells.
• Remember, cell structure fits cell function!
REVIEW:
CELL DIFFERENTIATION AND STEM CELLS
• Stem cells:
are undifferentiated cells that
can differentiate into specialized
cells and can divide to produce more
stem cells.
• The are used to replace old/dead
cells.
• Help with personalized medicine
and regeneration of tissues.
– Example: Pigs and transplants
https://www.youtube.com/watch?v=evH0I7Coc54
https://www.youtube.com/watch?v=p14AUxXlE-w
REGULATING CELL DIVISION
• 1. Apoptosis, or, Programmed Cell Death
– About 50-70 billion cells undergo apoptosis daily
• 2. When cells come into contact with other cells, they stop growing.
– Cells will divide rapidly at sites of injury (such as a cut or broken bone)
– Cells can be turned “on” and “off”
• 3. Cyclin: is a group of proteins that regulate timing of cell division in eukaryotic cells
– There are different type of cyclins that are preset at different times during cell division
– They are responsible for turning cell division “on” and “off”
• 4. Regulator Proteins: control internal and external processes before the cell can go
through cell division
– Internal: respond to events inside the cell, such as chromosome replication or mitotic spindle
formation
– External: responds to events outside the cell, such as growth factors
CANCER
• A disorder in which some often body’s own cells lose the ability to control growth
• Cancer cells do not respond to the signals that regulate the growth of most cells
• As a result cells divide uncontrollably and form masses of cell, called tumors
• A common defeated gene, p53, a internal regulator protein, fails to control cell
division
– Activates DNA repair proteins
– Halts cell division where necessary
– Initiates Apoptosis
– Prevents angiogenesis (blood vessel formation)
• Damaged or defective p53 genes cause the cells to stop responding to “on” and “off”
signals, often resulting in cancer
CANCER
• Differences between benign/malignant/metastatic tumors
• What are carcinogens?
• What are oncoviruses?
•
https://www.youtube.com/watch?v=BmFEoCFDi-w
•
https://www.youtube.com/watch?v=8LhQllh46yI
MEIOSIS
CHROMOSOMES
• Homologous chromosomes
– Two chromosome that contain the same genes (one comes from mom and one from dad)
– They don’t have identical genes on them, but the genes control the same function
• Diploid and Haploid
– Is a term used to describe cells in terms of their number of chromosomes
– Somatic Cells are Diploid= 2N: Bot sets of homologous chromosomes (46)
– Gamete Cells are Haploid= N: One set of chromosomes (23)
http://learn.genetics.utah.edu/content/chromosomes/intro/
MEIOSIS
OVERVIEW
• Meiosis is a process of reduction division in which the number of chromosomes per cell is
cut in half and separated into homologous chromosomes. They are both diploid cells
• It only occurs in gametes (sperm and egg cells)
• There are two distinct divisions – Meiosis I and Meiosis II
• Meiosis is similar to mitosis except for prophase 1
– What is the difference between a somatic and gamete cell?
– Why would they be different?
MEIOSIS
PROPHASE 1
• Each chromosome pairs with its corresponding homologous chromosome to form a tetrad
• Tetrad: two different sets of two sister chromatid or four chromatids
• Crossing over: the homologous chromosomes exchange portions of their alleles to produce
new combination of alleles
• Crossing over leads to greater genetic diversity in our populations: this is why no two
people look alike
MEIOSIS
OVERVIEW
• Meiosis 1:
– The two homologous chromatids
separate similar to mitosis forming
two new cells
– This produces two new cells each
containing 2 chromatids (4
chromosomes per cell)
• Meiosis II:
– The two cells contain 4 chromatids
in prophase II
– The result is four haploid
daughter cells that have 2
chromosomes each
https://www.youtube.com/watch?v=t
oWK0fIyFlY
MEIOSIS QUIZ
DIFFERENCES BETWEEN
MITOSIS AND MEIOSIS
• Mitosis: results in two genetically
identical diploid cells, meiosis produces
four genetically different haploid cells
• Mitosis: allows an organism’s body to
grow and replace cells, asexual
reproduction
• Meiosis: results in four haploid daughter
cells that have 2 chromosomes each
• Meiosis: used for sexually reproducing
organisms to produce gametes
http://www-tc.pbs.org/wgbh/nova/assets/swf/1/how-cells-divide/how-cells-divide.swf