Have you ever noticed that fruit flies don’t all look alike? If you look closely, you may see that they can have red eyes or white eyes.
Like all living organisms, fruit flies grow and reproduce. In Lesson 3.01, you learned mitosis is the process by which a cell divides into two daughter cells, each of which has the same number of chromosomes as the original cell. In Lesson 3.02, you were introduced to meiosis, the process by which organisms produce gametes. In this investigation, you will simulate mitosis and meiosis in fruit flies. Be sure you have fully investigated lessons 3.01 and 3.02 before beginning this assignment.
Materials:
16 pipe cleaners of 2 different colors and 4 matching lengths
String
O-shaped cereal
Marker
Procedure:
Part 1: Modeling Mitosis:
Copy the mitosis chart and add your name to the presentation. The circles you see represent a fruit fly body cell in different stages of the cell cycle.
Take out your pipe cleaners (to represent chromosomes). One color will represent the chromosomes inherited from the mother and one color represents the chromosomes inherited from the father. Use the same length of pipe cleaner for homologous pairs. You should have two sets of four different lengths of pipe cleaners.
Begin by assembling a diploid set of chromosomes for a fruit fly as they exist during most of interphase. A diploid set contains pairs of homologous chromosomes. Each chromosome at this point will be a single strand. You will have an extra set of each length and color left over. Here is a diploid set: Take note:
What is the diploid number of chromosomes in a fruit fly?
How many homologous pairs of chromosomes does a fruit fly have? (review this video for a review of chromosome numbers)
In late interphase, the amount of DNA doubles. That means each chromosome now doubles. Select a matching pipe cleaner (same length and color) for each chromosome and slide both through a piece of cereal. You now should have a set of eight doubled chromosomes arranged in homologous pairs.
Review the mitosis diagrams page 3 of Lesson 3.01 and move the chromosomes through the rest of the steps on your board.
Take a picture of each stage and place it in the appropriate circle in your diagram. Example:
This is a sample image of the # of chromosomes for a Spider Mite, not a Fruit Fly.
Fill in Tables 1 and 2 with the correct information
Table 1: Cell cycle and mitosis in fruit flies
Step Number of
Cells Number of chromosomes in
each nucleus Number of homologous pairs
in each nucleus
Interphase
Cytokinesis
A diploid set of human chromosomes contains 23 homologous pairs (46 chromosomes)
Table 2: Cell cycle and mitosis in humans
Step Number of
Cells Number of chromosomes in
each nucleus Number of homologous pairs
in each nucleus
Interphase
Cytokinesis
Part 2: Modeling Meiosis:
Meiosis is the process of producing sex cells with a haploid set of chromosomes. Haploid means half the number of chromosomes as the original cell. A haploid cell contains one chromosome from each homologous pair.
Copy the meiosis chart and add your name to the presentation. The circles you see represent a fruit fly body cell in different stages of Meiosis.
Begin by assembling a diploid set of chromosomes for the fruit fly as you did in Part 1. Place the chromosomes, in homologous pairs, in the first nucleus on your chart.
Like mitosis, before meiosis begins, the chromosomes double. Add a similar pipe cleaner to each chromosome and attach it with a piece of cereal as you did in part 1.
Unlike mitosis, which only has one cell division, meiosis has two divisions. Using the meiosis diagram Module 3 as a guide and move your chromosomes through Meiosis I and Meiosis II, taking pictures along the way.
Table 3: Meiosis
Step Number of
Cells Number of
chromosomes in
each cell Number of
homologous
pairs in each cell Diploid or
haploid
number?
Start of Meiosis
End of Meiosis I
End of Meiosis II
Conclusion Questions:
Write your answers in complete sentences.
What is the purpose of mitosis? What is the purpose of meiosis?
Why is it important for a cell to duplicate its DNA before it divides in two?
You have 23 pairs of chromosomes in your body cells. Why do your chromosomes occur in pairs? Where does each chromosome in the pair come from?
A dog’s diploid number of chromosomes is 78. How would the number of chromosomes in the dog’s body cells compare to the number of chromosomes in its gametes?
What happens to the homologous pairs of chromosomes in meiosis I?
What are the two main events that occur in meiosis (not included in this simulation) that leads to genetic variation in the gametes?
Why do siblings not look identical even though they are from the same mother and father?
