Mitosis and Meiosis Modeling Activity
Learning Objectives:
 To explain how DNA is transmitted to the next generation via mitosis
 To explain how DNA is transmitted to the next generation via meiosis followed by fertilization
 To describe the similarities and differences amongst the processes of mitosis and meiosis
 To understand how meiosis and crossing over leads to increased genetic diversity
 To comprehend the evolutionary significance of all of these processes
Procedure:
1. One of the characteristics of living things is the ability to replicate and pass on genetic
information to the next generation. Cell Division in individual bacteria and archaea usually occurs
by binary fission. With your partner, discuss the mechanism of binary fission and the end results
of this process. Be sure to discuss what functions cell division serves for a single celled organism.
2. Cell division in eukaryotes is more complex. As we have studied in the past, this process is called
mitosis. It requires the cell to manage a complicated process of duplicating the nucleus, other
organelles, and multiple chromosomes. Obtain an Allium cepa (onion) root tip slide and examine
this slide using a microscope. Be sure to observe cells in prophase, metaphase, anaphase, and
telophase.
3. After examining the onion root tip slide, return the microscope and slide back to the proper
location. Return to your seat and discuss the following questions with your partner.
a. How did you develop from a single-celled zygote to an organism with trillions of cells?
b. How does the genetic information in one of your body cells compare to that found in
other body cells?
4. Obtain a chromosome bead set, a dry erase board, and a marker.
5. Use the material obtained in step 4 to model a diploid animal cell with 4 chromosomes as it
undergoes each of the stages of mitosis. You will need to draw the stages of mitosis in the
conclusion questions (do not do so now because you will not have enough time). You may
want to take pictures of them now as you model to compare back to. Discuss what is
occurring during each stage with your partner while using the following terms: chromosomes,
sister chromatids, centromere, kinetochore, centrosome, spindle fibers, diploid, somatic cells.
6. After finishing modeling the stages of mitosis, discuss the following questions with your partner.
a. Why is it important for DNA to be replicated prior to cell division?
b. If a cell contains a set of duplicated chromosomes, does it contain any more genetic
information than the cell before the chromosomes were duplicated?
c. How do chromosomes move inside a cell during division?
d. What is the significance of the fact that chromosomes condense before they are moved?
e. How are the chromosome copies, called sister chromatids, separated from each other?
f. What would happen if the sister chromatids failed to separate?
7. Now imagine this is a germ cell. Model the cell as it goes through the 2 cycles of meiosis. You
will need to draw the stages of meiosis in the conclusion questions (do not do so now because
you will not have enough time). You may want to take pictures of them now as you model to
compare back to. Discuss what is occurring during each stage with your partner using the
following terms when appropriate: homologous chromosomes, sister chromatids, centromere,
kinetochore, centrosome, spindle fibers, crossing over, chiasmata, synaptomenal complex, tetrad,
gamete, germ cell, diploid, haploid, independent assortment, segregation, random fertilization.
Mitosis and Meiosis Modeling Activity- pg. 2
8. After finishing modeling the stages of meiosis, discuss the following questions with your partner.
a. When is the DNA replicated during meiosis?
b. How do sexually reproducing organisms produce gametes from diploid progenitors?
c. What is meant by independent assortment?
d. What are the outcomes from independent assortment and crossing over?
e. How does the distance between two genes or a gene and a centromere affect crossover
frequencies?
f. Are homologous pairs of chromosomes exact copies of each other?
g. What happens if a homologous pair of chromosome fails to separate, and how might this
contribute to genetic disorders such as Down syndrome?
Free-Response Extension Questions: 10 points total
1. Mitosis and meiosis are similar processes with very different functions. You modeled a diploid
cell with 4 chromosomes. Draw the stages of mitosis and meiosis for this cell.
2. Explain 3 similarities and 3 differences between mitosis and meiosis.
3. Many organisms reproduce asexually using either binary fission or mitosis. You have just
modeled this process and visualized the resulting daughter cells of mitosis. Apply your
knowledge of binary fission and mitosis to explain the evolutionary advantages to organisms that
undergo asexual reproduction.
4. Other organisms reproduce sexually by alternating episodes of meiosis and fertilization. You
have just modeled the process and resulting daughter cells of meiosis.
a. Once again, connect what you saw from your models today to explain the evolutionary
advantage of sexual reproduction.
b. Cite the specific aspects of meiosis that provide this advantage that are not available in
mitosis or binary fission. For each aspect mentioned, explain in detail how this
characteristic of meiosis provides this evolutionary advantage.
5. Explain how asexually reproducing organisms still exhibit change over time.