Meiosis Manipulatives
(Teachers – talk students through the modeling; as a student handout, delete photos on page 3 & 5)
In this activity we will use
“pop-it beads” to help us
consider the wonders of
sexual reproduction!
Introduction: Whether you are a plant or an animal, a fungi or a protist, if you
reproduce sexually, you also do meiosis. Whether you pronounce this as me-oh-sis or
my-oh-sis, it works the same way. Both parents contribute equal amounts of genetic
material the first cell of life. That DNA is copied, folded into chromosomes, and evenly
separated in every cell division that grows and develops the organism.
For sexual reproduction, one particular line of cells will duplicate the DNA strands, fold
them into chromosomes, and divide it twice, producing sex cells with have the DNA you
started with.
So what is meiosis? Meiosis is the special type of cell division that produces gametes!
Gametes are sex cells, the sperm and egg in animals, and the pollen and ovules in
plants. Gametes are “haploid” which means they have half the genetic material (DNA,
Chromosomes) than we would find in all the other body cells.
Want some more detail? All life forms that reproduce sexually follow a similar pattern.
Both parents contribute equal instructions in the form of the DNA. The DNA contains
the genes and packages itself into chromosomes. Chromosomes are helpful because
they package the genes so they can be evenly divided among the sex cells.
Let’s review some vital vocabulary:
DNA, gene, chromosome
homologous chromosome
maternal and paternal
diploid and haploid
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Final detail: Meiosis is reduction division. That fancy phrase just means that a diploid
(2n) cell undergoes two divisions, so our duplicated DNA from one cell gets cut in half
and placed in four cells. We call the resulting cells “haploid” gametes, having half the
genetic material as the original cell. Why does it make sense for gametes to be hapoid?
Sketch the human reproductive cycle placing mitosis and meiosis in context.
Models for Chromosomes
Modeling Material
How is it like a real
chromosome?
How is it NOT like a real
chromosome?
Yarn
Pipe Cleaner
Pop-It Beads
Modeling Meiosis
What do we mean by modeling?
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First, reach in nucleus bag and pull
out one small, medium, and large
chomosome of one color,
AND one small, medium and large
chromosome of the other color.
(Your kit may have chromosomes 3,5,7 beads in
small, medium and large chromosomes).
Next, pair up chromatids of same size and
color, so you have six X-shaped
chromosomes.
You are now modeling
--replicated DNA folded into chromosomes
--dipoid (2n) number of 6
--one set of 3 chromosomes from ma and
one set of three chromosomes from pa.
--different sized chromosomes (small,
medium, large) containing different genes.
It’s pretty obvious that sexual reproduction
requires two parents. What is less obvious is
that to make the sex cells we must evenly
distribute genetic information that was
inherited from the previous parental
generation. Something happens in the first
phase of meiosis that is really amazing. The
“ma” and “pa” chromosome of matching
structure.
To model this, match these “homologous
chromosomes” up in any possible pairing of
large, medium and small chromosomes from
both parents in the “sister chromatids” form.
Sister chromatids are held together by centromeres,
and of course, in an actual chromosome, instead of
plastic beads, we would have one long strand of DNA
wrapped and folded around numerous little protein
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spools called histones.
Also recognize that the pairing of maternal and paternal
Chromosomes is unique to meiosis (does not happen in
mitosis). These matching pairs of chromosomes are
called homologous chromosomes.
Now move the chromatid pairs through Prophase and
Metaphase of the first division of meiosis. Simply line up
the homologous chromosome pairs along the midline of
the cell.
Sketch your results in space to the right, 
using shading or coloring to distinguish
maternal and paternal chromosomes.
This pairing of homologous chromosomes sets the stage for even
distribution of instructions from ma and pa. When the homologous
chromosomes match up, they sometimes get so entangled that
segments of DNA on adjacent homologous chromosomes bread and
are glued back on the wrong chromosome.
This is called “crossing over” and adds to genetic diversity, but we
will better understand this when we finish our modeling! Crossing
over is just one of many ways we get genetic variation from meiosis!
Now move the chromosome pairs through the first
separation of the genetic material, by pulling apart
the homologous chromosomes into two haploid cells.
This is called Anaphase I of meiosis, when the
Homologous chromosomes separate.
Sketch your results in space to the right, 
using shading or coloring to distinguish
maternal and paternal chromosomes.
Each cell should now have three chromosomes of three different types (sizes).
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To complete meiosis, move the chromosomes
through the second division of genetic material.
After this division we end up with four cells each
with three chromosomes.
To do this, we must split our (imaginary)
centromere and separate the sister chromatids of
each chromosomes.
One possible outcome is shown the right, 
But there’s an 87.5% chance yours look different!
Each chromatid of the pair goes to a different sex
cell, making four haploid gametes.
Questions to Consider:
1) What is the diploid number of organisms from our imaginary organism?
2) What is the haploid number of chromosomes for our imaginary organism?
3) What is the diploid and haploid number of chromosomes in humans?
4) As the chromosomes separate in the two divisions of meiosis, what determines which
chromosomes end up in the resulting gametes? (Compare the chromosomes in your
resulting gametes to those resulting from other groups.)
5) The number of different chromosome combinations in the gametes is calculated as 2n
where n is the haploid number. For our model, n = 3, so 23 = 8.
Sketch all 8 possible (different) chromosome combinations.
 What is the significance of this?
6) As a class, let’s assume that half of the room was making sperm, and the other half of
the room was making egg. Let’s make a couple offspring. That sperm from there and
that egg from there, toss chromosomes on the floor. One zygote! Again, randomly pick
chromosomes from that egg there and that sperm there, boom, another zygote. Look at
the resulting chromosomes of these imaginary siblings.
 What is the significance of this?
7) Start over and model meiosis with “crossing over” happening once or twice.
 What is the significance of this?
On-line animations of Meiosis:
http://www.dartmouth.edu/~cbbc/courses/movies/meiosis.html
http://highered.mcgraw-hill.com/sites/0073031216/student_view0/exercise14/meiosis_movie.html
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