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Meiosis - Period 2 Group 2

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by

Donna Huynh

on 13 January 2014

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Transcript of Meiosis - Period 2 Group 2

Meiosis
& Sexual Reproduction
Dive into the microscopic world of meiosis as you find out how organisms reproduce!
Created by your friendly neighborhood AP Biology students:
Period 2 Group 2
Billy Zhang
Donna Huynh
Nicholas Tchan
Miranda Chan
Sabrina Dieu
Jacklyn Liu
*cue 80's disco synthetic music to make presentation snazzier*
Play-Doh Activity!
Materials!
Gather up these materials before you start this super cool activity!
Clay
You need red and blue clay (Ask Mr. Velekei for Play-Doh).
Paper & Scissors
String & Scissors
The clay will be used to make the chromosomes!
This will act as the cell!
You will need to cut out a large oval shape using one piece of white paper.
A piece of string will be used as the spindle fibers that will pull apart the chromosomes during anaphase!
Step
Roll out four pieces of
blue
clay into a snake shape. Two should be long (~3 ½ inches) and two should be short (~2 ½ inches).
Cut out four 4-5 inches of string for the spindle fibers.
Procedures!
Lay down the piece of oval-shaped white paper that will act as the cell.
Step
Connect the two long pieces together near the center and do the same for the short pieces!
Repeat this step for the
red
clay!
Step
You should end up with 4 pairs of chromosomes and spindle fibers. In this phase, each chromosome is replicated to form double-stranded chromosomes.
Prophase 1:
Cross one chromatid with the other color chromatid, so they connect each other. This state is called the
synapsis
.
Meiosis is actually very similar to mitosis in the sense that they both go through "I.P.M.A.T."
I
- Interphase
P
- Prophase
M
- Metaphase
A
- Anaphase
T
- Telophase
However, meiosis does
two
cycles of
I.P.M.A.T.
, but
does not repeat interphase
!
I.P.M.A.T.P.M.A.T.
Step
Pair up each chromosome with its
homologous
chromosome (same length, but different color).
The pairing of these chromosomes will produce two tretrads. A
tetrad
is a group of four sister chromatids (two pairs of chromosomes).
Step
Each color will represent the chromosome of a parent (
Red
=Mother
Blue
=Father).
Step
At the point(s) where they cross, cut it with scissors and exchange the piece(s) of chromatids.
This step is called
crossing over
!
Metaphase 1:
Take the four strings (spindle fibers) you cut earlier and loosely tie one to each of the four sister chromatids.
Step
Step
Line up the pairs of homologous chromosomes side by side at the
metaphase plate
(middle of the cell).
Crossing over
is a process during meiosis where two chromosomes pair up and exchange sections of their genetic material.
Step
Anaphase 1:
Drag each pair of homologous chromosomes away from each other to separate them!
Telophase 1 & Cytokinesis
End of Meiosis 1
Meiosis 2
Step
Remove the strings from the chromosomes.
...and cut the paper in half to form two new cells!
Prophase 2:
Meiosis 2
is the most similar to mitosis, in comparison to meiosis 1, but there are two cells this time!
Anaphase 2:
Telophase & Cytokinesis:
End of Meiosis 2
Step
During prophase 2, the spindles start to form so prepare four more pieces of string!
Metaphase 2:
Step
Line up the chromosomes at the metaphase plate and loosely tie the pieces of string to each of the four chromosomes.
Step
Pull the sister chromatids from away from each other, while going towards the opposite poles.
Step
Remove the strings from the chromosomes!
Cut each paper in half again to form four cells.
The cells are in
nuclei form
, where each of the four daughter cells are genetically different from one another!
*Note that we have two sets of chromosomes: one set from the father (
blue
) and one set from the mother (
red
). Each set was originally from a single cell called a
gamete
.
Gametes
are reproductive cells, such as sperm or eggs. They are also haploid cells, meaning they only have ONE set of chromosomes each. Every other cell that isn't a gamete are called
somatic cells
!
When a sperm fuses with an egg, it creates a
zygote
, which is a fertilized egg! This process is known as
fertilization
.
Since a zygote has chromosomes from two gametes now, it is considered a
diploid cell
, meaning it has TWO sets of chromosomes!
diploid cells
haploid cell
Fun fact! A
karyotype
is a display of the chromosome pairs of a cell arranged by size and shape.
Do you see those X and Y chromosomes? Those are called
sex chromosomes
!
The other chromosomes are called
autosomes
.
Know that meiosis doesn't occur in all cells! Only diploid cells undergo this process since they have enough chromosomes to
REDUCE
.
Other organisms, such as plants, fungi, and bacteria, go through
asexual reproduction
, where a clone of the parent organism is made instead of offspring due to no exchange of genetic material.
cell membrane
Interphase:
Questions # 2
What is...?
Questions # 3
!!!!!!!!!!
Questions # 4
How many chromosomes are in...?
Questions...
Take the following mini-quiz to test your basic knowledge!
Questions # 1
What is the difference between...?
Has this presentation successfully allowed you to grasp the idea of
meiosis and sexual reproduction
?
(Hopefully yes)
Somatic cells
&
Gametes
?
Sex chromosomes
&
Autosomes
?

Asexual reproduction
&
Sexual reproduction
?
A
karyotype
?
Crossing over
?
Nuclei form
?
The lining of the chromosomes does not have to be in a specific order. It is random, which creates and
independent assortment
!
Independent assortment
is the process of random assortment of chromosomes during anaphase I of meiosis. This is important because it results in a variety of genetically unique gametes.
In other words, with independent assortment, offspring are able to receive different sets of genes, resulting in different looking people!
Why is
independent assortment
important?
How is
meiosis 2
similar to mitosis?
A
gamete
?
A
zygote
?
A
sperm cell
at
meiotic anaphase 2
?
The End.
Music Credits:
Module - Fantasy is Real
Perturbator - Miami Disco
Full transcript