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Warm Up
1. Do all living things grow and develop?
2. Which type of cells have a nucleus?
3. What information does the nucleus
store?
4. Do you think cells grow like we do?
Explain why or why not.
Agenda
Objective: SWBAT: Explain what happens
during the cell cycle and how the nucleus
divides during mitosis AND determine the
number of chromosomes a cell has following
cellular division.
Go over quizzes
Mitosis cards
Mitosis Hand jive
Phase cards
Try to put the cards in order
What are the diagrams on the cards?
How did you decide what order to put
them in?
What do you think is happening at the
end of this process?
Unit 4
Mitosis and Meiosis…
How things grow and develop!
1. How do we grow?
a) The process starts with our cells
Our cells can only grow so big. Then they
have to divide to produce more cells.
Example: When a fetus is developing and
growing, it’s cells are dividing
What happens when a cell gets too
big?
If your mom got pregnant with sextuplets
(meaning 6 babies at once!),the house would
get REALLY crowded. Anyone would have a
hard time taking care of all those kids!
2. What happens when a cell
gets too big?
a. When a cell is small, the information
stored in that DNA is able to meet all of
the cell’s needs.
b. When a cell increases in size, the
DNA has a harder time performing
all of its functions.
3. What are Chromosomes?
a. Chromosomes are made up of DNA
b. Every organism has a certain
number of chromosomes
Example: Humans have 46
c. Most the time, you cannot see
chromosomes because they are
spread out in the nucleus
Chromosomes are only visible
during cell division
3. What are chromosomes?
d. Before a cell divides, it has to copy
it’s genetic information.
e. DNA is a type of nucleic acid that
carries proteins and all the cell’s
genetic information
DNA controls what a cell does
In Eukaryotic cells, DNA is stored in the nucleus
f. DNA is bundled up into structures
called chromosomes
4. What is the structure of a
chromosome?
a. When they become visible, you can
see that each chromosome is made
up of two identical parts, called
chromatids
b. Each “sister” chromatid is
connected in the center by a
centromere
Draw & Label the Chromosome
5. How does a cell divide?
a. Cell Cycle: series of events that a cell
goes through as it grows and divides
b. Interphase is what happens in a cell before it
divides. “Inter” means between, so
interphase means between phases
Step 1: The cell increases in size and makes
new proteins and organelles
Step 2: DNA is synthesized (copied)
Step 3: The cell finishes everything it needs to
do before it divides
5. How does a cell divide?
c. One of the most important events is the
“M” phase
d. During the M phase, two things occur:
Mitosis: the division of a cell’s nucleus
AND
Cytokinesis: the division of a cell
“Cyto” = cell
“kinesis”= movement
The Cell Cycle
What is this?
Watch a couple movies
Mitosis 1
BrainPop Mitosis
Exit Ticket
1. What is a chromosome made of?
2. What must a cell do before it divides?
3. __________ is when the nucleus of a
cell divides.
4. Why do cells divide? Explain in
complete sentences.
Warm Up
1. How do we grow?
2. What happens to the DNA when a cell
gets too big?
3. DNA is a type of ________________?
4. How many cells are produced after
cytokinesis?
Agenda
Objectives: SWBAT: Identify the types of cells that
undergo mitosis as well as the type of cells that
undergo meiosis AND identify why approximately
half of an individual’s DNA sequence comes from
each parent.
Review Mitosis and learn about Meiosis
Mitosis Hand Jive
Go over quizzes
Exit Ticket
Review of Cell Division
Before a cell becomes too large, it divides to
form two “daughter” cells.
What must a cell do before it can divide?
Copy its DNA!
What divides in the process of mitosis?
The Nucleus
1. Mitosis
a. Mitosis is the division of a cell’s nucleus
b. It’s a part of the M-phase of the Cell Cycle
-
The Cell Cycle: is the entire life span of a cell
from creation to division
Before a cell can divide, it goes through the
period of growth called Interphase. DNA is also
copied
Mitosis Hand Jive
Review of Chromosomes:
a. Each chromosome is a
single, long structure that
only becomes the “x” shape
after DNA replication.
b. A human has 23 pairs
(46 total) chromosomes
- After DNA is copied, we
have 46 pairs (92 total!)
chromosomes!!!!
6. Put these pictures in order
Parent cell
During
Interphase the
cell prepares for
mitosis and DNA
is replicated
centrioles
spindle fibers
centrosome
nucleus with
DNA
1. Prophase
a. Prophase is the first phase of mitosis.
b. During Prophase the chromosomes
bundle up and become visible.
c. The centrioles split up and take
positions on opposite sides of the
nucleus.
d. The nuclear envelope that surrounds
the nucleus breaks down
Prophase
2. Metaphase
a. Metaphase is the second stage of
mitosis
b. During metaphase, chromosomes
line up in the middle of the nucleus
c. The centrioles are on opposite sides
of the nucleus and the spindle fibers
attach to each chromosome
Metaphase
3. Anaphase
a. Anaphase is the third phase of
Mitosis.
b. During Anaphase the chromosome
pairs separate and move toward
the opposite poles or sides of the
cell.
Anaphase
4. Telophase
a. Telophase is the fourth and final phase of
mitosis.
b. During Telophase the chromosomes begin
to loosen and form bundles of material that
are hard to see.
c. The cell membrane starts to pinch down
and divide into two cells in Telophase.
d. The nuclear envelope also reappears and
begins to form around the two new nuclei.
Telophase
5. Cytokinesis
a. Cytokinesis happens AFTER mitosis
b. This is when the cell’s cytoplasm
divides to create two identical cells
c. After this process, each new cell will
begin Interphase and the Cell Cycle
will start all over again
Cytokinesis
Review
• If a cell has 12 chromosomes, how
many will it have after mitosis?
• How many daughter cells are produced
after mitosis?
• What types of cells go through mitosis?
Sexual vs. Asexual Reproduction
Do all organisms reproduce in the same way?
No
What type of organisms reproduce sexually?
Animals and Plants
What type of organisms reproduce asexually?
Bacteria
All Living Things Reproduce
*This is one of the 7 characteristics of living things*
a. Most plants and animals
reproduce by sexual
reproduction.
b. In sexual reproduction,
cells from two different
parents combine to
form the first cell of the
new organism.
What is Asexual Reproduction?
a. Other organisms reproduce asexually,
where a single parent produces offspring
that are identical to the parent.
b. What is Mitosis, asexual or sexual
production?
- Asexual. It’s one parent cell producing two
identical cells from itself.
What organisms reproduce
asexually?
c. Most prokaryotes, like bacteria,
reproduce asexually.
d. Asexual reproduction is the primary
form of reproduction for single-celled
organisms such as bacteria.
Asexual Reproduction
What are diploid cells?
a. Asexually Reproducing organisms have
diploid cells.
b. A diploid cell is a cell that has two copies
of each chromosome. Diploid means two
sets (2n) of chromosomes.
Exit Ticket
1. What happens in cytokinesis?
2. DNA is arranged in _______________.
3. If a cell has 4 chromosomes and goes
through mitosis, how many chromosomes
would it’s daughter cell have?
4. In asexual reproduction, offspring get their
genetic information from ______________.
Warm Up
1. If a daughter cell has 23 pairs of
chromosomes, how many pairs does the
original cell have? What living thing has 23
pairs of chromosomes?
2. A ________ cell has two full sets of
chromosomes.
3. What happens in asexual reproduction?
Agenda
Objectives: SWBAT: Explain that meiosis is
necessary for sexual reproduction AND
Determine the number of chromosomes a
cell has following the process of meiosis.
Notes on Meiosis
Video and Questions
Exit Ticket
Mitosis hand-jive review!
What are Haploid Cells?
a. Sex cells (eggs and sperm) contain only
one copy of chromosomes.
b. Haploid means one set of chromosomes.
A haploid cell is a cell that only has one
set (1n) of genes.
c. Eggs have an X chromosome and sperm
cells can have either an X or a Y
chromosome.
Haploid vs. Diploid cells
What happens before Sexual
Reproduction?
b. Cellular division happens two times to
produce sex cells. DNA is copied one time,
but the total number of chromosomes is
divided two times.
What happens before Sexual
Reproduction?
a. Offspring inherit half of their genetic
information from each parent
b. That means sex cells will only contain half
of the parents’ DNA
What is Meiosis?
a. Meiosis is the type of cellular division that
results in 4 daughter cells with half the
number of chromosomes.
• Only occurs in organisms that can reproduce
sexually.
• Produces haploid cells
What happens to the # of
chromosomes?
a. In Meiosis, the nucleus divides four times
leaving each nuclei with half the number of
chromosomes.
b. Example:
•
•
•
•
Parent cell- 2n
Replication- 4n or 2 pairs
Mitosis- 2n
Meiosis- n
DEMO!
I need 4 volunteers 
Meiosis and Sexual Reproduction
a. Meiosis occurs to make gametes (sex
cells) which combine to create an
offspring.
b. Sexual reproduction is what makes
living things different from one another.
The fertilized cell is different from both the
mother's egg and father's sperm because it
has two different sets of DNA.
What is Genetic Variability?
a. Genetic Variability means that the
genes are different from each other.
b. Meiosis produces genetic variability
among organisms.
Do these 3 boys look identical
to their mom?
What are the Advantages of
Meiosis?
a. Sexual reproduction increases the
amount of variation within a species.
b. This variation improves the chance
that a species will adapt to its
environment and be able to survive.
Example
The number of owls increase in a park
and the amount of mice decreases
rapidly. However, the quickest mice are
able to escape the owls. In time, more
fast mice are born, allowing them to
survive. They adapted to the change
and survived because they were
genetically different.
What are the Disadvantages
of Mitosis?
a. Organisms that reproduce asexually
cannot develop much variety, because
they are just "copying" the parent.
b. Since they are all exactly the same, the
organisms will probably not survive a
disaster.
White Board Review
How many chromosomes do we have
total?
How many chromosomes did we get from
each parent?
Meiosis produces how many
daughter cells?
4
Which type of cellular division
allows for genetic variability,
mitosis OR meiosis
Meiosis
A dog has 78 chromosomes in
each of its cells. One of its cells
goes through mitosis. How many
chromosomes will the new,
daughter cell have?
78!!!
Remember, a cell that has gone through
mitosis will have the same number of
chromosomes!
Write out
the correct
order of the
pictures
3, 2, 5, 1, 4
What type of cells has two
sets of chromosomes (2n) ?
Diploid
Sex cells are a type of
___________ cell because
they have half the number of
chromosomes
haploid
This is a picture of which
process?
LAST Question
What occurs AFTER mitosis in
the Cell Cycle?
Cytokinesis!
Exit Ticket
Exit Ticket
1. Diploid cells have twice as many
chromosomes as ______________ cells
2. Mitosis occurs in Asexual or Sexual
reproduction?
3. If a living thing has 20 chromosomes and it’s
cell goes through meiosis, how many
chromosomes will be in one of the new cells?
4. What is an advantage of meiosis?
Warm-Up
1. How many cells are produced by
Mitosis?
2. How many cells are produced by
Meiosis?
3. Mitosis is a form of _______________
reproduction
4. Meiosis is a form of ______________
reproduction
Agenda
Objectives: SWBAT: describe
“crossing over” and explain how it leads
to further genetic variability AND
evaluate the role of meiosis in
maintaining genetic variability.
Notes
Video Clips
What does Meiosis look like?
MEIOSIS I
MEIOSIS II
Possible gametes
Possible gametes
How do we get genetic
variation?
independent assortment of chromosomes
in meiosis.
Chromosomes pair up randomly, and then split
into two new cells
That means two traits can be inherited
independently from one another
Example: a cat's color and tail length
How do we get genetic variation?
random fertilization of gametes (sex
cells)
Any sperm can fertilize any egg
There are trillions of different
combinations of chromosomes
How do we get genetic variation?
When chromosomes cross-over in
meiosis
What is crossing-over?
Crossing over occurs when genes
from one chromosome are exchanged
with genes from another chromosome
results in new combinations of genes
Also called recombination
What does Crossing-over look
like?
Crossing over is
important because it
allows for variation
in the genes we
inherit from our
parents.
Crossing over
Video Clips
http://www.goldiesroom.org/video_archi
ve.htm
http://www.brainpop.com/science/cellul
arlifeandgenetics/genetics/
Compare Mitosis and Meiosis
Diagrams