Name: _________________________________
Modeling Meiosis Activity
Introduction:
In this activity, you will model the events that take place in sex cells when egg and sperm are made. The
chromosomes you built in the last activity represent chromosomes that would be found in primary sex cells (found in
testes and ovaries in humans). As your gamete formation diagram shows, part of sexual reproduction is making egg
and sperm (gametes) from these primary sex cells. This happens through a process called meiosis. In this activity,
you will examine how chromosomes move and sort themselves in meiosis.
Materials: (for each group of two students)
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6 complete chromosome models
1 piece of chalk
Stages of Meiosis Handout
Meiosis I
Procedure
1. Draw a large circle (about 2 feet in diameter) on your lab bench. This represents the cell membrane of your
primary sex cell.
2. Draw a smaller circle inside the larger circle (about a foot in diameter). This represents the nuclear membrane.
3. Late Interphase: Place all of your chromosomes anywhere within the nucleus - do not pair homologous
chromosomes. At this stage, the DNA is technically still in a form called chromatin and has not yet coiled up into
chromosomes. Your model, however, suggests the DNA is in chromosomal form. This stage represents late
interphase because the cell has already replicated its DNA during the S phase. Draw how your chromosomes
look in this stage in the circle labeled Late Interphase” on the attached Meiosis Diagram Worksheet.
How many chromosomes are present at this point?
Are the homologous chromosomes present in the same cell?
Are the sister chromatids present in the same cell?
Explain the difference between your model and the diagram of interphase.
4. Prophase 1: Pair each chromosome with its homologous chromosome. Erase the inner circle. This represents
prophase 1. The nuclear membrane breaks down at this point. This is also where crossing over occurs (more on
this later). Draw how your chromosomes look in this stage on your worksheet.
5. Metaphase 1: Place your paired homologous chromosomes in a straight line down the middle of the cell (see
diagram). This represents metaphase 1. Draw this stage on your worksheet.
You likely randomly placed the maternal or paternal homologous chromosome on the left and the other on the
right for all three pairs of chromosomes. In nature, this is in fact random.
Name: _________________________________
Draw how you lined up your chromosomes in the Option 1 column. Label whether each chromosome is maternal
or paternal.
Draw two other options for how the maternal and paternal chromosomes could have lined up in Metaphase 1.
Now move your homologous chromosomes (remember they always have to be paired side by side) around in the
cell to create 2 other options for how the homologous chromosomes could line up. Draw these in the table
below.
Option 1
Option 2
Option 3
The fact that there are multiple options for how homologous chromosome can line up in Metaphase 1 is called
independent assortment.
How many total options are there for how three pair of homologous chromosomes can line up? How about 23
pair? (the actual number in human cells)
Sign Off: ______________________________
6. Anaphase 1: Separate your homologous chromosomes into 2 rows on either side of the cell. Each row consists of
1 of each of the different homologous chromosomes. This represents anaphase 1. Draw this stage on your
worksheet.
7. Telophase I: After anaphase, nuclear membranes begin to form around each set of chromosomes. A new cell
membrane also begins to form down the middle of the cell, eventually dividing the cell into two daughter cells.
Model this by drawing the newly formed nuclear membranes and cell membranes. This represents telophase I.
Draw this stage on your worksheet.
8. Cytokinesis I: Meiosis I ends with the chromosomes de-condensing into chromatin and the cells completely
dividing. Model this by completely dividing your cell into two cells. You do not need to draw this stage on your
worksheet.
Explain the difference between your model and the diagram for cytokinesis I.
Name: _________________________________
Analysis Questions
1. Describe the events of meiosis I in your own words.
2. How many maternal and paternal chromosomes does each of the daughter cells have?
Daughter Cell 1
Daughter Cell 2
Maternal
Paternal
Explain if this is this the only option for your cell?
3. How many chromosomes does each daughter cell have at the end of meiosis I?
4. What was separated during meiosis I? What was not separated?
Separated:
Not separated:
5. How many alleles for each trait does each daughter cell have?
Meiosis II
Procedure
1. Prophase II: At the end of meiosis I, 2 complete daughter cells have formed. Meiosis II begins with the chromatin
condensing back into chromosomes and the nuclear envelopes disappearing again. This represents prophase II.
Model this by erasing your nuclear membranes in both daughter cells. Draw this stage on your worksheet.
2. Metaphase II: Line up the 3 duplicated chromosomes vertically down the middle of each cell. This represents
metaphase II. Draw this stage on your worksheet.
3. Anaphase II: Pull the sister chromatids apart in each cell and move each of the sister chromatids to opposite
sides of the cell. This represents anaphase II. Draw this stage on your worksheet.
4. Telophase II: After anaphase, nuclear membranes begin to form around each set of chromosomes. A new cell
membrane begins to form down the middle of each daughter cell, eventually dividing each cell into four total
cells. Model this by drawing the newly formed nuclear membranes and cell membrane. This represents telophase
II. Draw this stage on your worksheet.
Name: _________________________________
5. Cytokinesis II: Meiosis II ends with the chromosomes de-condensing into chromatin. This represents cytokinesis II.
Model this by completely dividing you cells into two cells. You do not need to draw this stage on your worksheet.
6. Store your chromosomes in a bag for use in the next lesson.
Analysis Questions
1. Describe the events of meiosis II in your own words.
2. What separated during meiosis I? During meiosis II?
Meiosis I:
Meoisis II:
3. How many chromosomes are present in the original cell? In the cells at the end of meiosis I? In the cells at the
end of meiosis II?
Original:
Meiosis I:
Meiosis II:
4. Indicate how many chromosomes (maternal or paternal) were in each cell at the end of meiosis.
Daughter Cell 1
Daughter Cell 2
Daughter Cell 3
Daughter Cell 4
Maternal
Paternal
Explain if other maternal and paternal combinations were possible?
5. How many alleles for each trait does each daughter cell have?
6. Write the genotype for each of the four gametes in your model. Use the symbols for the alleles for each
chromosome.
7. Honors Only: Determine all the other possible genotypes for gametes given the different options for how
homologous chromosomes can line up in metaphase I.
8. Honors Only: Had crossing over occurred between the long homologous chromosomes, what other options
would exist for genotypes in your gametes?