Name: ________________________________________
MEIOSIS MANIPULATIVES
Introduction:
You are going to study the process of meiosis by working with chromosomes from a mythical organism known as
Sevenia. Sevenia‘s diploid cells have a chromosome number of four. You will follow these procedures listed below and
write the answers to the questions as they arise.
Materials:
-4 pieces modeling clay of four different colors
-1 large oval cut from white paper
-4 smaller ovals cut from white paper
-1 pair of scissors
-8 tootsie rolls
-1 long piece of red yarn
-2 short pieces of red yarn
-8 small pieces of white string
-16 small white stickers
Procedure:
1. From the front table, obtain half of a tub of clay of 4 different colors, eight tootsie rolls from your teacher, and the
other materials listed above.
2. Cut out a large white oval from the butcher paper at the front of the room. Cut out four small ovals from the scratch
apper.
3. Place the large white oval paper in the center of your desk. The boundary of the paper is the cell membrane. This
oval represents one precursor sex cell of Sevenia.
4. Make a smaller circle on the inside of the white circle with the large piece of red yarn, which will represent the
nuclear membrane.
5. Now you will set up the genome. You are going to create a diploid cell, which will contain two pairs of
chromosomes. Roll each piece of clay between your hands to form an elongated piece like a snake. You will have
four chromosome models. Make two of the chromosomes about four inches long and the other two about 6 inches
long. The shorter pair is Pair 1 and the longer pair is Pair 2.
Note: A chromosome is a tightly coiled strand of DNA and within each chromosome there are many, many
genes. The chromosomes within each pair are homologous. Homologous chromosomes are the same in size and
function but they do have different alleles. For instance, the homologous chromosome may contain the same gene
such as eye color but the allele form might be for one blue and the other brown.
6. You will look at four traits of the Sevenia. You will look at their location on each chromosome. On your white
stickers, write G, g, C, c, B, b, L, and l. Then stick them onto your clay chromosomes according to the picture on the
next page. The letters stand for either fur color, fur straightness, eye color, or eyelash length. See the chart on the next
page.
Chromosome #2
Chromosome #1
Chromosome #3
Chromosome #4
Alleles
Fur Color
G (green fur)
g (yellow Fur)
Genes on PAIR 2
Eye color
B (blue eyes)
b (red eyes)
Alleles
Fur Type
c (straight fur)
C (curly fur)
Genes on PAIR 2
Eyelash Length
L (long eyelashes)
l (short eyelashes)
Remember that we are looking at 4 pairs of alleles and 4 genes
Question A: What are the GENES we are looking at?
Question B: What are the ALLELES we are looking at?
Question C: What is the chromosome number for Sevenia?
7. INTERPHASE
During Interphase, each chromosome is replicated. We won't be replicating the DNA in its chromatin form, like it is
actually replicated during interphase. Just keep this in mind so that you don't get confused as to how DNA actually
copies itself.
a)
Using the remaining clay, create matching chromosomes the same shape and color as the original.
b)
Connect sister chromatids at the centromere by pinching them together.
8. PROPHASE I
a) Put 2 tootsie rolls in the white circle to represent centrioles.
b) Pair up each newly replicated chromosome with its homologous chromosome (meaning with the chromosome
with the same letters, capitol or lowercase nonwithstanding) You will now have two tetrads that contain 4 sister
chromatids each, 8 chromatids in all.
c) Now that the homologous chromosomes are near each other, crossing over can occur. In each tetrad, trade one
allele between two non-sister chromatids by overlapping chromosome arms to form a crossover (i.e., break off
some of one of the chromatids, along with the letter label, and swap it with the same location (same letter) on the
other chromosome.
9.
METAPHASE I
a)
The nuclear membrane disintegrates. Pull the red yarn out of the cell and put it aside.
b)
Line the two tetrads end to end across the center of the cell on what would be the metaphase plate.
c)
Move the two tootsie rolls to each pole of the cell.
d)
Tie a piece of string representing spindle fiber to the centromere of each chromosome on one end and to the
centriole on the other.
Question D: Was there a reason that certain color chromosomes ended up on the same side, or was it random? Why or
why not?
10. ANAPHASE I
a) Separate each tetrad and use the spindle fibers to pull the homologous chromosomes to opposite poles of the
cell.
11. TELOPHASE I
The nuclear envelope begins to reform around each new group of chromosomes. The cleavage furrow begins to form.
You will not be able to recreate the cleavage furrow. Just remember this is when it forms.
a) Use the smaller pieces of red yarn to recreate the developing nuclear envelopes.
12.
CYTOKINESIS I
Cytokinesis (cytoplasm division) occurs to form two daughter cells.
a) Take two of the small white circles and put the two chromosomes from each pole into each circle. Recreate
the nuclear envelope with the red yarn in each of the two cells.
Question E: Are the two daughter cells identical (in genetic make-up)? Why or why not?
13. Prophase II + Metaphase II
a) Line up the chromosomes in each cell end to end along the metaphase plate and put tootsie rolls at each pole
to represent centrioles.
b) Take away the red yarn nuclear envelopes.
c) Tie the spindle fibers (white string) to the centromeres on one end and the centrioles on the other. MAKE
SURE YOU ATTACH A PIECE OF STRING TO EACH SISTER CHROMATID!
14. Anaphase II
a)
Separate the two sister chromatids.
b)
Use the spindle fibers to move them to opposite poles.
15. Telophase II and Cytokinesis II
a.
Begin to form new nuclear membranes around each set of chromosomes with the red yarn.
b.
Put each new set of chromosomes in their own white circle, creating 4 new cells.
Genotype:
Phenotype:
Question F: Write the genotype and phenotype beneath each of the resulting daughter cells in the diagram above (what
alleles would the offspring get from this parent if they came from that particular cell?).
Question G: How many chromosomes are in each daughter cell?
How does this compare with the original cell?
Question H: Are these cells haploid or diploid?
Question I: Do any of the cells have the same combination of genes?
Why or why not?
Question J: Why is genetic variation important?
16. Repeat all steps WITHOUT CROSSING OVER any of the chromosomes.
Question K: Draw a picture of your daughter chromosomes below, indicating which color ended up where.
Question L: Do the four daughter cells differ? If yes, how do they differ? Why is this important?
Conclusion/Wrap-Up
Question M Why do you resemble one parent more than another?
Question N Why do you look like your mom or your dad?
Question O: How can you resemble both of your parents, but not be a clone of either?