Transcript Surface Area & Cell Cycle

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What cells divide?
Why do they divide?
How do they divide?
How often do they divide?
Etc.
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Multicellular organisms grow by adding more cells,
not by growth of individual cells.
• The cells of a baby are basically the same size as an
adult
• Babies are smaller because they have fewer cells.
 1)
In order to remain small
(reasons will follow)
 2) Grow
 3) Replace dead or dying cells.
 4) Repair damaged tissue healing.
 5) Reproduce
 Small
cells are much more efficient.
• Small cells have enough cell membrane for
its cytoplasm and organelles.
• Small cells can produce enough proteins to
survive.
 Stem
Cells
• What are stem cells?
• Why are they important?
• How can they be used?
• Why are people upset about using stem cells?
• What is your opinion.
DNA
stores genetic information and
the instructions for all cell activities.
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DNA + histones = chromatin. In the nucleus, DNA
exists as chromatin for most of its life.
Tightly coiled chromatin is called a chromosome.
Genetic Information in the Cell
 Chromosomes
• Have a specific length, shape and pattern,
and code for specific traits
Before a cell divides, it must make a copy of its DNA so
the new cell has all the necessary genetic material to
exist. This is called replication.
Replicated chromosome = 2 sister chromatids joined by
a centromere.
 Get
out the chromosome worksheet from
yesterday.
 I will be checking it!
 Manager
 Recorder
 Spokesperson
1.
Multicellular organisms grow by
increasing cell number, not by the
increase in cell size.
a) True
b) False
1.
What is not a reason for cell division.
a) To remain small
b) Growth
c) Repair dead tissue
d) To go through photosynthesis or respiration.
1.
How do we count the number of
chromosomes?
a) By the chromatids
b) By the centromeres
c) By the number of X shaped DNA packages
1.
How many chromosomes is in this
picture?
1.
How many chromotids is in this picture?
1.
Draw a homologous pair of
chromosomes.
1.
A female has which chromosomes?
a) XX
b) XY
c) YY
1.
How many pairs of chromosomes do
you have?
1. 1
2. 22
3. 23
4. 46
1.
How many chromosomes do you have?
1. 1
2. 22
3. 23
4. 46
 Cell
Cycle - The time from the
beginning of one cell division to the
next.
 Occurs
 Cell
in eukaryotic cells.
contents (DNA and organelles)
double and cell divides into two
complete and identical cells.
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The cell cycle consists of four phases:
• G1: Most of the cell’s growth & activity
• S: chromosome replication takes place
These 3 phases
make up what is
called
INTERPHASE
• G2: final preparations for cell division
• M: Mitosis-division of nucleus and Cytokinesis-division of
the cytoplasm
 Contact
Inhibition – healthy cells will not
divide if they are surrounded by other
cells.
 Checkpoints
– Healthy cells have
automatic stops during the cell cycle.
They must receive a go-ahead signal
before the cycle will continue.
Cancer
- loss of control over
cell cycle
• Cancer cells continue to divide even when
they come into contact with other cells.
• Cancer cells never stop at checkpoints.
• Cancer cells destroy good cells by
consuming all available nutrients.
A
general term used for the G1, S, G2
phases of the cell cycle combined.
 Cell spends most of its life (90%) in
Interphase.
 Nucleus
breaks apart so chromosomes
can move.
 Chromosomes organize and separate so
that each “daughter” cell gets a complete
and identical set of genetic information.
 In each cell, a nucleus forms to surround
the genetic information.
 Answer the following questions:
• What is the purpose of mitosis?
• Mitosis is the division of what?
• During which stage of the cell cycle does the cell spend
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most of it’s life?
If the parent cell has 46 chromosomes, how many
chromosomes do each of the daughter cells have?
A crayfish has 200 chromosomes, how many
chromosomes would daughter cells produced in mitosis
have?
In which stage of mitosis are chromosomes lined up in
the middle of the cell?
In which stage of mitosis are the sister chromatids pulled
apart?
 In
plants, cytoplasm is divided by a
cell plate, or a new cell wall.
 In animals, cytoplasm is divided by
pinching its cytoplasm in half. This
pinching forms a cleavage furrow.
PINCH
CELL PLATE
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Two daughter cells
Genetically identical to each other
Rate
of cell division depends
on a number of factors:
• Type of cell
• Environment
• Cellular controls
 Some
cells rarely divide.
• Examples: Heart, nerve, and spinal cord cells.
• Injuries to these tissues are often permanent.
 Some
cells rapidly divide throughout
life.
• Examples: Skin cells, red blood cells, and
digestive tract
Temperature
• Cold temps can slow cell division
• Warm temps can speed cell division
• Extreme high temps can denature enzymes and
stop cell division
 Nutrients
• Lack of nutrients will slow cell division.
 Dehydration
• Lack of water will stop/slow cell division
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 Create
a video explaining mitosis.
 MUST HAVES:
• Each step of mitosis (interphase, prophase, metaphase,
anaphase, telephase, and cytokinesis).
• Each part that is involved: Nucleus, DNA, chromosomes,
chromatids, centromere, spindle fibers, and centrioles.
• The number of centromeres, chromosomes, and
chromatids in each step.
• Each person must explain at least one step.
 Chose
 Blue-headed
 Duck
one from each column:
wrasse
leech
 Grizzly Bear
 Leafy sea dragon
 Red kangaroo
 Sand scorpion
 Amoeba
 Salmonella
 Whiptail
lizard
 Brittle star
 Meadow garlic
 Spiny water fleas
 Answer
the following questions:
• Mitosis is the division of what?
 Wat about cytokinesis?
• A pharent cell has 46 chromosomes, how many
will each daughter cell have?
• the name of cells that go through mitosis?
 What are some examples of these cells?
• Based What is on what you learned yesterday, is
mitosis asexual or sexual? Why do you think this?
Asexual
Reproduction
Sexual
Reproduction
One parent cell.
Two parent cells.
New cell will have same
number of chromosomes as
parent cells.
New cell will have ½ the
chromosome number of the
parent cell.
New cells contain the exact
same DNA as the parent.
New cells will contain a
combination of DNA from both
parents.
Repeated mitosis
Meiosis and Fertilization
Somatic Cells
Gametes
These are body cells such as
blood, skin, muscle, etc.
These are cells that are used
for reproduction.
Produced by mitosis.
Produced by meiosis.
 Meiosis
is needed to make haploid cells
from diploid cells.
 Haploid cells are needed for sexual
reproduction.
 Sexual reproduction is needed for
genetic diversity.
 Meiosis
I
• Interphase (like in the cell cycle)
• One diploid cell divides to form two haploid cells.
 Meiosis
II (looks a lot like mitosis)
• Two haploid cells divide to form four haploid
cells.
Diploid
Haploid
2n
1n
Cells that have 2 copies of
each chromosome.
Cells that have 1 copy of each
chromosome.
One copy came from mother
cell and one came from father
cell.
The chromosome came from
either the mother or the
father.
• Zygote – A single diploid cell that is produced by
union of two gametes (egg and sperm in humans).
• Repeated Cell Cycles will form a multicellular
organism, made of many genetically identical
diploid cells.
• Meiosis will occur in specialized organs (ovaries
and testes in humans) to produce gametes.
• Fertilization will join two gametes to produce
zygote and the cycle starts again.
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Meiosis
• Crossing Over – Recombinant chromosomes can be
formed that contain genes from both parents.
Crossing over
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Fertilization
• Random Fertilization – Any sperm could fertilize any
egg if they came into contact.
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Independent Assortment
• Chromosomes can line up in any formation during
metaphase I so many combinations of parents’
chromosomes can be formed.
• In humans, each chromosome pair could line up 2
ways. We have 23 chromosome pairs. That gives us
223 = about 8 million possible gametes per parent.
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Random Fertilization
• In humans, each parent could make about 8 million
different gametes. That give us
8 million x 8 million = almost 70 trillion possible
children per couple.