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Focus 8: Mitosis & Meiosis

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Nicole Martin

on 23 March 2018

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Transcript of Focus 8: Mitosis & Meiosis

Mitosis & Meiosis
Focus 8
BOCW
Why do cells need to reproduce, anyway?
Essential Question
What are the phases of the CELL CYCLE?
The Cell Cycle
The life cycle of the cell, including THREE major stages.
The Cell Cycle
Mitosis
BOCW
Microscopy
BOCW
Meiosis
Purpose: Perform life functions and prepare to divide.
5
Phases of the
Cell Cycle
3 Parts of
Cell Cycle:
G Phase
o
When a cell will leave the cycle and quit dividing
May be a temporary resting period.
Not on the table - put in your notes.
Part 1
Interphase
G Phase
1
Major Organelles/Parts of Cells:

Entire cell, organelles needed for function.
Events:
Cell is performing its normal functions.
Accumulating materials through cell membrane

Known as...
Growth Phase
S Phase
Major Organelles/Parts of Cells:

Nucleus and Nuclear membrane

Events:
DNA is making a duplicate copy of itself.

Known as...
Synthesis (DNA)
G Phase
2
Major Organelles/Parts of Cells:

Nucleus
Events:
Chromatin begins to coil preparing for mitosis and nuclear division

Known as...
More growth
M Phase
Major Organelles/Parts of Cells:

Centrioles
Spindle fibers
Nucleus


Nuclear membrane
Cytoplasm
Vesicles (plants)
Part 2
Mitosis
Four Stages:
1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
Part 3
Cytokinesis
Cytokinesis
Major Organelles/Parts of Cells:

Cytoplasm

Events:
Division of the cytoplasm

Animal: Fibers are pulling to close in the cell membrane and form two daughter cells
Plants: Vesicles bind together forming cell plate that divides cell
Important Vocab
Somatic Cells
Any body cell that is not a gamete (sex cell).
Chromatin
Mass of genetic material.

Found in nucleus of cell.

Condense to form chromosomes.
Chromosome
Genetic material

Condensed chromatin

Contains double
helix.
Nuclear Envelope
The membrane of the cell's nucleus.
Centriole
Made of microtubules

Function in cell division

Only in animal cells
Spindle Fibers
Move chromosomes during cell division.

You will need this Vocab when we begin discussing
tomorrow!
MITOSIS
Write in your
NOTES
Left Side Activity
Color & Label the CELL CYCLE!!!
Interphase
Cytokinesis
Mitosis
G1 S
G2
Prophase
Metaphase
Anaphase
Telophase
(Interphase)
(Interphase)
(Interphase)
(Mitosis)
(cytokinesis)
Exit Ticket
During which step of the cell cycle do the chromosomes and genetic material double in preparation for division?

In what stage does division actually occur?
Splitting in two!!!
What are the phases of the Cell Cycle?
Essential Question
What are the steps of mitosis?
Yesterday we learned about the...
Cell Cycle
there are two main sequences:
1. period of growth

*Interphase
2. period of division
*Mitosis
*Cytokinesis
Mitosis
Process by which 2 daughter cells are formed, each containing a complete set of chromosomes

Steps of
Mitosis
PMAT
Prophase
First and longest phase of mitosis

Long, stringy chromatin coils up into visible chromosomes

Nucleus disappears

The centrioles migrate to opposite ends of the cell

Interphase
Parts of the cell cycle BEFORE mitosis
Gets cell ready for mitosis.
Regular nucleus with chromatin.
Centrioles in cytoplasm.
Metaphase
Prometaphase
"Before metaphase"
Spindle fibers form and extend from centrioles.
Chromosomes are doubled and ready for division.
Doubled chromosomes attach to the spindle fibers by their centromeres

Chromosome
chromatid
each half
doubles in S phase
centromere
holds the two SISTER chromatids together
Both sister chromatids held together by a centromere.
Line up on midline (equator) of the cell.
Anaphase
Centromeres split apart and sister chromatids separate from each other

Spindle fibers pull chromatids apart.
Telophase
Chromatids reach the opposite poles of the cell

Spindle fibers disappear.
Nucleus reappeards.
Cytokinesis
Part of the cell cycle AFTER mitosis.
Division of the cytoplasm.
Mitosis
Challenge
Anaphase
Prophase
Metaphase
Telophase
Cytokinesis
Cytokinesis
Plants vs. Animals
animal
Plant
Honors: Cell Cycle Table
G1
S
G2
Mitosis
Cytokinesis
Interphase
Left side activity
Mitosis foldable
Prophase
Metaphase
Anaphase
Telophase
Front: Title
Inside: Image and major events.
Exit Ticket
Why is it important that the chromatids DUPLICATE themselves during the S phase of the Cell Cycle.
In which step of mitosis do the sister chromatids separate?
Essential Question
How can I use a microscope to make observations of mitosis?
Parts
of a
Microscope
Ocular Lens
Eyepiece you look through.
Provides 10X magnification
Arm
Holds up the eyepiece.
Place one hand here when carrying.
Nosepiece
Revolves to change the magnification.
Objectives
Three different lenses to provide magnification.
Options: 4X, 10X and 40X
Stage
Surface where the slide is placed.
Stage Clips
Hold the slide in place.
Coarse Adjustment
Always the BIG knob.
Moves stage up and down for focus.
Big movements.
Fine Adjustment
Always the SMALL KNOB.
Moves stage for minute adjustments.
Diaphragm
Opening in the bottom of the stage for the light to pass through.
Light
Provides back light to view the slide.
Base
Bottom of the microscope.
ALWAYS place one hand here to carry,
Proper use of the
Light
Microscope
Carry it Safely
Two hands
1- Arm
2- Stage
How to Focus a microscope
1. Start with SMALLEST OBJECTIVE!
2. Center image on lens.
3. Use COARSE knob to focus first.
4. Use FINE knob to focus second.
5. When CLEAR switch to next highest objective.
Be Careful! You Can break this!
Always have a friend watch the slide to ensure you are not pushing on it with the objective! This can smash the objective of the slide!!!
Stay with your group and STAND to ensure no one knocks over a scope.
BEWARE of dangling electrical cords!
All done? Let's clean up properly!
1. DO NOT wrap cord around scope!
2. Use a rubber band to wrap cord around itself and secure it.
3. Place a cover over the miscrope.
4. Carry it PROPERLY back to the cart and place it there.
5. Go DIRECTLY back to your seat.
Exit Ticket
What was the most challenging part of using the microscope?
BOCW
What are the four stages of mitosis and what is THE major event of each?
PROPHASE - Chromatin shortens into chromosomes.
METAPHASE - Chromosomes line in in middle.
ANAPHASE - Spindle fibers sep. chromosomes into chromatids and pull apart.
TELOPHASE - Chromatids reach opposite sides.
Essential Question
What are the steps of meiosis and what are the major features of each?
Identify that step!
Mitosis Review
Prophase
iNTERPhase
anaphase
Cytokinesis
1st Period - Mitosis Flow Chart
3rd Period - Mitosis Flip book
30 Minutes:
Two Types of Cell Divison
Mitosis
Meiosis
Produces 2 IDENTICAL daughter cells with the same chromosome number as the parent cell

Produces 4 DIFFERENT daughter cells with half the chromosome number as the parent cell

two Types of Cells
DIPLOID
2n – two sets of chromosomes
One from mom and one from dad

Human body (somatic) cells have 46

HAPLOID
N – half the diploid number of chromosomes

Human sex cells (gametes) have= 23

Homologous Pair
Pair of chromosomes that are the same size, shape, and carry the same genetic information (genes).

One inherited from mom the other from dad.

Diagram of Chromosomes.
23 pairs
=
46 chromosomes
Meiosis
Function:
Produce gametes/ gametic cells =egg and sperm

Location:
Ovaries and Testes

Key Feature:
Daughter cells only have half the number of chromosomes as parent cells

Reductive Division!
What is Meiosis About?
Meiosis allows the creation of unique individuals through sexual reproduction.

egg = 23
sperm = 23
total = 46
Why is Meiosis Necessary?
To get the CORRECT numbe of chromosomes into each new zygote!
Before Meiosis...
DNA replicates during the S phase of the cell cycle

Each chromosome is replicated

Prophase 1
SAME as in mitosis!
Crossing over may occur!
Tetrads form.
Important Vocab
Tetrad
A pair of chromosomes together
Crossing Over
Chromosomes may swap sections
More On Crossing Over
Exchange of information when tetrads of homologous chromosomes touch each other
Pieces can break or jump to other chromosomes when they touch or are close: CROSSING OVER

Increases
Genetic
Variation!
Metaphase 1
Same as in mitosis.
Tetrads, not individual chromosomes, line up on the equator of the cell

Anaphase 1
Spindle fibers contract and pull tetrads apart

Entire double stranded chromosomes are pulled to opposite ends of the cell

Telophase 1
Cytoplasm divides
Daughter cells are diploid

4 steps
4 steps
Summary of Meiosis 2
The mechanics of Meiosis II are identical to Mitosis

Each diploid daughter cell produced by Meiosis I divides again to produce four different haploid cells

Left Side Activity
Fill in MITOSIS & MEiOSIS
Note the differences!!!!
Factors Contribute to
GENETIC VARIATION
3
Random separation of chromatids through the 2 divisions

Independent Assortment
Crossing-over multiplies the already huge number of different gamete types produced by independent assortment.

Crossing
OVEr
The zygote that forms a new individual is created by the random joining of two gametes

Random Fertilization
LOTS of diversity here!
Exit Ticket
HOW does meiosis increase genetic variation and WHY is this important?
Comparing
Mitosis & Meiosis

BOCW
What are the three ways that meiosis can increase genetic variation?

Explain/define each!
Essential Question
Differentiate between spermatogenesis and oogenesis.
Paths of Meiosis in Humans
2
Meiosis produced three polar bodies and one viable egg.
Oogenesis
In females.
Produces only a few hundred mature eggs over a lifetime.

Spermatogenesis
Process that creates eggs!
In males.
Produces four viable sperm.
Produces roughly 250,000,000 sperm per day.

Process that produces sperm!
Random Fertilization
Remember... any sperm could get to the egg first! This means that a baby could get its chromosomes from any number of sperm or egg combinations!!!
L.s. Activity #1
Fill in the cells to show the steps of mitosis & meiosis.
Label each step.
Glue into left side of INB.
Need help? Grab a textbook!
L.s. Activity #2
Create a T-chart comparing and contrasting mitosis & meiosis. BE THOROUGH!
mitosis
meiosis
similarities
Quick Video Review
1st Period: Whiteboard Challenge
3rd period: Meiosis Webquest
Vocabulary Review
Exit Ticket
List three major differences between mitosis & meiosis.

What is one similarity?
Reproduction
BOCW
Differentiate between spermatogenesis and oorgenesis, where does each occur?
Essential Question
What are the differences between sexual and asexual reproduction, and what are examples of each?
Asexual Reproduction
Requires only one parent
Offspring have 100% the same chromosomes as the parent.
Offspring are exact clones
Most unicellular organisms
Mitosis
Binary Fission
Some unicellular organisms simply double everything and split in half.
Common among prokaryotes!
Plant Cuttings
Removing a piece from a living plant and cultivating it to create a new plant.
The new plant is exactly the same as the old one!
Budding
A new individual develops from an outgrowth of a parent, splits off, and lives independently.

Common in the Hydra, a unicellular organism.
fragmentation
A single parent breaks into parts that regenerate into whole new individuals.

Starfish do this!
Planaria as well
Benefits of
Asexual Reproduction
Time efficient (faster)
No need to find a mate.
Requires less energy
Disadvantages of
Asexual Reproduction
NO VARIATION!!!
All organisms are exactly the same!
More susceptible to DISEASE
Less able to ADAPT to environment
Negative impact on SPECIES SURVIVAL!
Sexual Reproduction
Requires two parents.

Each donates half the genetic information.
Offspring share the characteristics of each parent.
Meiosis.
Sexual Reproduction is Very Common!!!
All Animals
Fish
Mammals
Amphibians
Birds
Reptiles
Insects
Crustaceans

Plants
Flowers are the reproductive organs of plants!

Internal Fertilization
External Fertilization
Egg and sperm meet INSIDE the body of the female.
Mammals (including humans), birds, reptiles, insects and spiders.
Egg and sperm meet OUTSIDE the body, in the environment.
Fish, some amphibians, plants and fungi.
Placental Animals
The baby develops INSIDE the body of the female before birth.
A placenta enables exchange of nutrients with the growing baby.
Oviparous Animals
Almost
all
mammals
Laying eggs from which the baby is born.
Birds, fish, reptiles, most amphibians and few mammals
Just in case you're interested...
(don't take this note, unless you want to)
Monotremes
Mammals that lay eggs.
Platypus and echidna only.
Only in Australia and New Guinea.
Spores
Released by certain species to fertilize eggs.
Some plants, fungi.
Pollination
Released by plants to fertilize female organs of other plants.
Benefits of
Sexual Reproduction
MORE VARIATION!!!
With so many unique individuals in the population we are MORE LIKELY TO SURVIVE!
Disadvantages of
Sexual Reproduction
Takes more energy AND time
Need to find a suitable mate
Create A T Chart
Sexual vs. Asexual Reproduction
Be sure to include mitosis & Meiosis
Exit Ticket
A killer apple disease infects a farmers crop. Which apple species is most likely to survive? The one that is sexually reproducing or the one that is cloned (monoculture)?

EXPLAIN WHY!
Full transcript