Name_____________________________________ Date ___________ Per.____
“Meiosis”
A. OBJECTIVE:
Discover and understand key steps in meiosis, and possible misunderstandings about the meiosis using
yarn representing the chromosomes.
B. IDENTIFICATION:
1. Each single piece of yarn represents one chromosome
a persimmon piece equals one chromosome inherited from the mother;
a yellow piece equals one chromosome inherited from the father.
2. Two pieces, held together equals one chromosome duplicated into two new strands (chromatids), each
of which becomes a duplicate chromosome when the centromere splits at the beginning of anaphase.
C. INVENTORY: Check your chromosomes. Make sure that you have the correct number.
1. 2 LONG persimmon pieces
2. 2 LONG yellow pieces
3. 2 SHORT persimmon pieces
4. 2 SHORT yellow pieces
D. PROCEDURE: Use your yarn chromosomes and arrange them on your lab table for each step of
meiosis when you are finished with each step, your instructor will go over the correct picture so
you can draw it in your notebook. Please note that you HAVE to draw your step after using your
string. You will have 8 separate pictures in your notebook. There is not enough string to go
through each step all at once:
1. Start with Prophase 1 – Arrange your chromosomes so that the homologous chromosomes are
arranged together and crossing over is illustrated. Hint: Cut off a piece of each chromosome and
tie them on the chromosome on the other homologous chromosome of a different color.
2. Metaphase 1 – Homologous chromosomes line up on the cell equator. Unlike mitosis, the
homologous chromosomes line up NEXT TO each other so that PAIRS are pulled apart in the
next step.
3. Anaphase 1 – Spindle fibers (like in mitosis) pull the homologous chromosomes to opposing poles
of the cell.
4. Telophase/ Cytokinesis 1 – Nuclear envelope begins to reform around new set of chromosomes. 2
cells are formed. Both of these cells will undergo Meiosis 2 below.
The following process (Meiosis 2) occurs JUST LIKE mitosis:
5. Prophase 2 – Cells organize from its previous division. Homologous chromosomes are still paired
together.
6. Metaphase 2 – Homologous chromosomes line up on the cell equator in a line.
7. Anaphase 2 – Spindle fibers pull homologous chromosomes a part and sister chromatids are pulled
to the poles of the cell.
8. Telophase/ Cytokinesis 2 – Nuclear envelope is formed, new cell begins to form. Since we started
with 2 cells at the start of Meiosis 2, 4 cells total will be formed.
E. DISCUSSION QUESTIONS:
1. Complete the table below:
Mitosis
Which type of cells undergo
each process?
Process to increase genetic
variance?
Steps in the process:
Meiosis
None
Product of each process:
(number of cells, identical
or not identical?)
2. Crossing over occurs in Prophase 1 of Meiosis. Why is crossing over important?
3. In autosomes (cells that undergo mitosis), 46 chromosomes exist in each cell. Every
sperm and egg cell (product of meiosis) has 23 chromosomes. Why is this important?
4. Define the following:
a. Haploid:
b. Diploid:
c. Homologous Chromosomes: