Name: ___Melanie Bellido_____________________
Meiosis Modeling Activity
Background Information
Meiosis is the process by which eukaryotic organisms produce egg and sperm having half the genetic
information (haploid) of the other cells in the organism’s body (diploid). You will notice some similarities
to mitosis but some definite differences in meiosis that result in genetic diversity in the gametes as well
as the offspring formed by the eventual fusion of the egg and sperm.
Two of the most noted differences in meiosis are that 1) there are two complete divisions resulting in
four daughter cells and, 2) meiosis has crossing over, an even that occurs in Prophase I that increases
genetic variation in the gametes. Crossing over occurs between homologous chromosomes. These are
the pairs of chromosomes in an organisms body that carry genes for the same trait located at identical
positions on the two chromosomes. Even though they carry the same gene they may, however, possess
different alleles for the gene which result in different forms of the trait.
Pre-Lab (3 points)
1. Draw a tetrad in the space below and label the following: centromeres, sister chromatids,
homologous chromosomes.
2. What are the two elements of meiosis that add variation to our population? (Hint: one occurs
in prophase I and the other in metaphase I).
Recombination and independent assortment
3.
Which of the chromosomes #2-5
could be homologous with
chromosome #1? Explain your
answer.
#5, they match in
length, and gene location.
Homologous means they are
identical.
Lab:
1. First view the presentation on my message board under “Class Resources” and then
“Resources for Portfolios”.
2. After you have viewed the presentation, gather your required materials. You will need 4 forks,
4 knives, 4 spoons, 6 rubber bands, and some twine or string to use as cell membrane. If you can
have two different types of flatware that would be best (for example: 2 forks, 2 knives, and 2
spoons that are different than the other set of 2 forks, 2 knives, and 2 spoons).
3. Your model cell consists of 6 chromosomes (3 homologous pairs). Use the string to form the
cell membrane for your cell(s). Begin with two forks, two knives, and two spoons (one of each
from each set) inside your string cell membrane as shown in the recording. Proceed through each
of the steps of meiosis using your flatware “chromosomes.” Use the textbook pages 324-325 for
help.
Phase
Modeling
Interphase
Replicate the DNA of your chromosomes by adding a second fork, knife, or spoon
to each existing fork, knife, and spoon. Hold each pair of “chromatids”
together with a rubber band (centromere).
Prophase I
Create tetrads (XX) by pairing homologous chromosomes (set them next to each other).
Model crossing over as best you can given the model we are using.
Line up your tetrads along the metaphase plate. Model independent assortment.
Metaphase I
Anaphase I
Telophase I
Cytokinesis I
Move the homologous chromosomes to opposite ends of the cell.
You should have three chromosomes, knife, fork, and spoon, (each composed of
two chromatids) in each of your two nuclei.
Divide your cell membrane so that you have two daughter cells (two string circles for
cells).
Prophase II
Metaphase II
Anaphase II
Telophase II
Cytokinesis II
Check to make sure that each of your two cells contains three chromosomes made up of
sister chromatids.
Line your chromosomes up along the middle of each of your cells.
Separate your sister chromatids (remove rubber band holding them together). Move one
sister chromatid from each chromosome to opposite sides of your cell.
You should now have four nuclei, with three single chromosomes in each of the cells.
Divide your cell membranes so that you have four daughter cells (use more string).
Data (8 points)
Take 4 photos OR create 4 drawings of your model as it looked in 4 different stages of meiosis
as described in the table above. Indicate which stage of meiosis is shown in each photo/drawing.
Include the photos or a scan of the sketches when you upload your lab to the drop box.
Conclusion (7 points)
1. Does mitosis more closely resemble meiosis I or meiosis II? Explain your answer.
its meiosis 2 because in this separation of sister chromatids occur which is very similar to
mitosis..
2. What is crossing over? When does it occur during meiosis? Why did you have difficulty
modeling this element of meiosis using your “chromosomes?”
Crossing over happens in prophase I. It occurs when 2 homologous chromosomes exchange
DNA between abject homologous chromatids. They are then no longer identical.
3. Think about your modeling. Visually, what is the major difference between the
separation of chromosomes between anaphase I and anaphase II?
In anaphase I homologous chromosomes separate while 2 sister chromatids separate.
4. What is independent assortment? When does it occur during meiosis? How did you
model this element of meiosis?
It is the shuffling of chromosomes.Independent assortment happens in meiosis I because
that's when the homologous chromosomes separate from each other and go into two
different cells.
5. Which part of meiosis, meiosis I or meiosis II, is responsible for reducing the
chromosome number by half in the cell?
Meiosis I in telophase I.