Download Gummy Worm Mitosis NAME___________________20PTS

Gummy Worm Mitosis
NAME___________________20PTS
Pre Lab Questions:
1. What are the 5 phases of the cell cycle?
2. What are the 4 phases of Mitosis?
3. What happens during Cytokinesis?
4. How is a gamete different from a somatic cell?
Mitosis -- How Your Body Makes New Cells
The production of such a large number of body cells is accomplished by many, many repeats of a cycle of cell division in
which one cell gives rise to two cells, each of which in turn gives rise to two cells, etc. Thus, cell division is needed for
growth.
Even in a fully grown adult, cells still undergo cell division.
The two cells that come from the division of one cell are called daughter cells.
Each of the daughter cells needs to have a complete set of chromosomes.
5. What are chromosomes?
6. Why does each cell need a complete set of chromosomes?
In each cycle of cell division, the cell first makes a copy of the entire DNA in each of the chromosomes.
After the DNA in each chromosome has been copied, the cell undergoes a type of cell division called mitosis, which
carefully separates the two copies of each chromosome to opposite ends of the dividing cell, so each daughter cell ends up
with a complete set of chromosomes.
Mitosis -- The Basics
Once the DNA of a chromosome has been copied, the two copies of the DNA form two chromatids which are attached to
each other at the centromere. These chromatids are often called sister chromatids because they are identical. During
mitosis the two chromatids of a chromosome separate and become independent chromosomes; one of these chromosomes
goes to each daughter cell.
To keep our model simple, we will begin by discussing mitosis in a cell that has only two chromosomes.
7. What value would represent this organism, (remember Humans are n=23)?n
These two chromosomes are a pair of homologous chromosomes. Both homologous chromosomes contain genes that
control the same traits (e.g. eye color and skin color). For each gene on a pair of homologous chromosomes, there may be
two different versions or alleles of the gene on the two different homologous chromosomes (e.g. an allele for brown eyes on
one chromosome and an allele for blue eyes on the other chromosome).
Modeling Mitosis
Introduction:
Students will model cell growth, mitosis and cytokinesis using gummy worms, paper plates, twizzlers
and licorices bites to represent the cell parts. Each chromosome will have 4 gummy worms joined at the
middle to represent the sister chromatids in a chromosome after the DNA has been replicated.
Materials:
A. 2 PAIRS of gummy worms of different colors (4 total)
(you can cut or tear some to show different sized homologues)
B. An unwound twizzler - these are the spindle (or kinetichore) fibers
You may also use spaghetti to represent these fibers
C. 2 red licorice bites – these are the centrosomes
D. Paper Plate- this represents the cell
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Procedure:
1. To indicate that you have a pair of homologous chromosomes, gummy worms will be the same colors.
Explain what the color represents, in terms of what it is for in the body. Students should be creative pick a trait for colors on chromosomes to represent (brown hair, blue eyes, widows peak, etc.)
8. Which traits do your gummy worms carry??
2. Use the cell parts to demonstrate how the cell undergoes Mitosis - Model the phases of the cell cycle
beginning with Interphase and moving through Mitosis to Cytokinesis. Model each stage with the candy
and photograph it using your iPad. Each group is responsible for a slideshow in iPhoto that represents
the phases of Mitosis! Please show me your models as you create each phase.
Mechanics of mitosis
In a living cell, when the cell is carrying out its normal activities, the DNA molecule of each
chromosome is a long tangled thread. Each human cell has 46 chromosomes (23 pairs of homologous
chromosomes). Obviously, it would be difficult to reliably separate the two copies of each of 46 long
tangled DNA molecules. Therefore, in preparation for mitosis, the DNA is condensed into compact
chromosomes, like those shown in the diagram.
The basic steps of mitosis, which ensure that each
daughter cell receives a complete set of
chromosomes, are as follows.
1. DNA is copied
2. DNA is condensed into compact chromosomes
3. Spindle fibers line the chromosomes up in the
middle of the cell.
4. Spindle fibers shorten to pull the sister
chromatids apart toward opposite ends of the cell.
5. The cell begins to pinch in half, with one set of
chromosomes in each half.
6. Two daughter cells are formed.
(For simplicity, the figures show cells that have
only 4 chromosomes (2 pairs of homologous
chromosomes), but the basic process is the same as
in human cells, which have 46 chromosomes.
Analysis: - Post Lab Questions on Mitosis
9. How is this type of cell division different from binary fission in Prokaryotes?
10. What would happen if a cell did not make a copy of its DNA before it divided?
11. Are the two homologous chromosomes genetically identical? Why not?
12. What do we call cells with 2 copies of every chromosome?
13. How many gummy worms would you need to accurately represent Prophase in a human?
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