CTU A Single Cell Divides to Produce Two Daughter Cells Worksheet


Meiosis Gizmo
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
1. During mitosis, a single cell divides to produce two daughter cells. What must happen in the original cell
so that each of the daughter cells has a complete set of chromosomes?
2. During sexual reproduction, two sex cells fuse to create a fertilized cell with a complete set of
chromosomes. What must be true about the number of chromosomes in each sex cell?
Gizmo Warm-up
Meiosis is a type of cell division that results in four daughter cells with half
as many chromosomes as the parent cell. These daughter cells mature into
gametes, or sex cells. In the Meiosis Gizmo, you will learn the steps in
meiosis and experiment to produce customized sex cells and offspring.
On the STEPS tab, click Male. You are looking at a germ cell, or a cell
that will undergo meiosis to become gametes.
1. Read the description of interphase at the bottom of the Gizmo. What happens to the cell at the beginning
of interphase?
2. Click on the DNA in the nucleus of the cell. Describe what happens.
3. Why is it necessary for the cell to grow and duplicate its DNA before the start of meiosis?
Activity A:
Steps in meiosis
Get the Gizmo ready:
● Make sure the STEPS tab is selected.
● If necessary, choose the Male cell. Click on the
DNA to copy it to proceed to prophase I.
Introduction: Unlike mitosis, which produces two identical daughter cells from one parent cell, meiosis creates
four unique daughter cells with half the amount of DNA as the parent cell.
Question: How does meiosis create four daughter cells from one parent cell?
1. Observe: (Prophase I) Click on the nucleus to break it down then click on the DNA to condense it into
chromosomes. Drag the centrosomes to the top and bottom of the cell.
A. How many chromosomes does this cell have?
Each chromosome consists of a pair of sister chromatids, tw
strands of DNA that formed when DNA replicated during
B. On the image to the right, ✏ Draw two lines connecting the
pairs of homologous chromosomes (chromosomes of
similar size with a matching set of genes). Click the image to
select EDIT to use the drawing tool.
In the Gizmo, drag the homologous chromosomes
Click Continue.
2. Observe: (Metaphase I and Anaphase I) – Drag the groups of homologous chromosomes to the
metaphase plate, then drag spindle fibers from each of the centrosomes to the chromosomes. Click the
centrosome to pull the chromosomes apart.
How do the chromosomes separate in anaphase I?
3. Compare: An image of the anaphase step in mitosis is shown to the right.
A. How does anaphase I in meiosis
differ from anaphase in mitosis?
B. At the end of anaphase I (meiosis), how many
chromosomes are on each side?
4. Observe: Telophase I and cytokinesis are the final steps of the first half of meiosis.
A. Describe what happens when you click on the
chromosomes during telophase I.
B. Click and drag on the contractile ring. Describe
what happened during cytokinesis.
5. Observe: Go through the steps of the second half of meiosis until you reach the end of telophase II,
following the instructions at the top right corner. As you proceed, answer the questions below. Use the Back
button if you need to see a step again.
A. Before prophase II begins, does the DNA in
the cell duplicate itself?
B. During metaphase II, do homologous
chromosomes pair up as in metaphase I?
C. How does anaphase II differ from anaphase I?
D. At the end of anaphase II, how many
chromatids are on each side of the cell?
E. Are all of the cells the same size?
The original parent cell is called diploid because it contains a complete set of homologous
chromosome pairs. Each of the four daughter cells is haploid, meaning that each contains half of
the original parent cell’s chromosomes. Each daughter cell contains one chromatid from each
homologous pair.
6. Observe: Click on the spermatids. Spermatids that formed from
meiosis will develop into mature male gametes called sperm cells.
Mature sperm cells have only a small amount of cytoplasm and use their flagella, or “tails,” to
propel themselves forward. Sperm are designed for one purpose, to deliver genetic material to
the egg cell during fertilization.
Activity B:
Comparing female
and male gametes
Get the Gizmo ready:
● Make sure the STEPS tab is selected.
● Click Reset.
Introduction: Although both male and female gametes contain genetic material from the parent organism,
they perform different functions. A male gamete delivers genetic material to a female gamete. The fertilized
female gamete, called a zygote, then grows into the offspring.
Question: What are the differences in meiosis between male and female cells?
1. Compare: Click on the Female button. For the female cell, proceed through meiosis until you reach the end
of anaphase I.
Up to this point, did you notice any differences between the development of male and female gametes?
2. Compare: Proceed through telophase I and cytokinesis I.
A. What do you notice about the size of the two
resulting cells?
B. How does this compare to the two cells at the end
of telophase I and cytokinesis I in male cells?
3. Compare: Continue through meiosis until you finish telophase II and cytokinesis II.
A. What do you notice about the four cells
B. What is the largest cell called?
The ovum is the largest cell in the human
body. In contrast, the sperm cell is the
smallest cell in the human body.
C. What are the small cells called?
Polar bodies are small cells that develop as a byproduct of meiosis in females. In humans and most
other animals, these cells play no significant role and soon die.
4. Think and discuss: Why do you think egg cells are large and sperm cells are small?

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