Name:_________________________________________________

screenshotDrosophilab

This simulation can be downloaded from http://www.drosophilab.com/, and does not need an internet connection to operate.   Download and install the program to your home computer or laptop, or to the school network.   You will be given a series of tasks to complete with the simulator, where you will need to take notes, gather data and draw conclusions about what you have observed.   You will also need to download the fly-file to complete the tasks; these are flies created by the instructor and not included with the downloaded program.

Task 1:  A Simple Monohybrid Cross

1)  In this experiment, you will start with a male and female that are both heterozygous for the vestigial wing trait. The abbreviation for the parents is vg+ for wild type (normal) and vg for vestigial wings.

exp1Show a punnet square for the cross of the two heterozygous parents:

vg+ vg x vg+ vg | Or use simpler notation Gg x Gg

What are your expected results based on the punnett square (percentages)?

 

 


2) In Drosophilab, select File >> New Experiment. Enter "TASK 1" in the Name field and leave the P1 generation as it is. Now click on the questionmark icon that says "Male"; in the load dialog select the file "TASK1-vgmale.fly". Do the same for the female by selecting "TASK1-vgfemale.fly"

Right click the white area that says "counting jars" and select "add jar". Enter Wild when prompted for a jar label. Next add a jar labeled "vg". Click "OK" to create the experiment.

3) You have now created an experiment along with your parental generation. To examine parent flies in the microscope, drag one of the fly icons to the panel labeled "microscope." You can rotate the fly by holding down the ctrl key and dragging and the slider can be used to zoom in. Draw your parents below and label the male and the female.

What is the main difference between a male fly and a female fly?

 

 

4) Now it is time to create a filial generation. The flies in the parental generation should already be red, indicating they will be used as parents for the next generation. If they are not red, right-click the icons and set as parent.

Now select Experiment >> New generation. In the dialog box, leave the generation name as it is and enter 20 as the number of offspring. Make sure that "Icons is selected as shown in the image.

Click OK to see the 20 offspring of your first cross.

screenshot

5) Click on each fly one by one and examine them. The word "wildtype" is used to denote a fly that has normal characteristics. Drop each of your wild type flies in the Wild Jar. Any fly with vestigial wings will go into the other jar.

How many OBSERVED wild flies did you have? _____ How many vestigial winged flies? _____

6) Out of 20 flies, based on the punnett square, how many would you EXPECT to be wild type? _____ vestigial winged? ____

7) The program has a built in Chi Square calculator, under the "tools" menu. Place your values in this calculator to see if you observed results match the expected one.

What is your Chi-square sum?__________ What is the Critical Value? _________

*Reminder: Your chi square sum must be below the critical value for you to accept the hypothesis.

8) If your original hypothesis was that your parents were both heterozygous for the vg trait, would you accept or reject the hypothesis?

 

Task 2: Backcrossing

1) What would happen if you took a vg vg fly from your offspring and crossed it with the parent from your first cross (vg+ vg)? What offspring would you get in this generation and in what proportion?

Cross is vg vg (vestigial wings) and vg + vg (heterozygote) or SIMPLY: gg x Gg

2) Empty your counting jars to continue the experiment and delete the row marked F1. Cross your parents again to create 10 offspring.

From the offspring (F1), find one that has vestigial wings. Set this fly as the parent and then click on one of your original parents in the P1 group that is the opposite sex and set as the other parent.

3) Under "experiment", click "new generation" which will show you the results of this cross.

How many wild type flies?___________ Vestigial winged flies? ____________ (observed)
How many were expected wild type flies? _______ Vestigial winged flies _________ (expected)

4).  Perform a chi square analysis to show that your hypothesis is supported (or rejected).

What is your Chi-square sum?_________ What is the Critical Value? ________
Is this a good fit or a poor fit? _______

5) Now choose a fly from the F1 generation that is wild-type (normal wings.) At this point, you don't know the genotype of this fly. Backcross it with a parent, create at least 20 offspring from this cross. Based on the offspring numbers, what is the genotype of this fly?

Explain how you know this.

 

Task 3:  Chromosomes and Alleles

1) Open the chromosome MAP.  You will see four sets of chromosomes with letters indicating a particular gene located on that chromosome.   Clicking on the letters will give you a description of the gene;  write below.

Sex Chromosomes (XY/XX)

w = _______________________________
rb = _______________________________
cv = _______________________________
t  = _______________________________
f  = _______________________________
B =_______________________________
Chromosome II

al = _______________________________
*Cy = _______________________________
b = _______________________________
pr = _______________________________
vg = _______________________________
L = _______________________________
c = _______________________________
Chromosome III

jv = _______________________________
se = _______________________________
th = _______________________________
cu = _______________________________
sr = _______________________________

Chromsome IV

ci = _______________________________
sv = _______________________________

*Why are some letters capitalized?

2) Open the chromosome editor and design a fly by changing any number of the alleles. Now that you have a better appreciation for the fly genotypes, explain the notation used to describe these traits:

What does a + mean?

Why are some alleles capital letters, and some lowercase? List all the traits of the fly that would be considered dominant.

 

Task 4: Sex-Linked Traits

1) What is your prediction if you cross a wild type male (XRY) with a mutant female (XrXr)?  Show the genotypes and the punnett square below.  What ratio is expected among your offspring.  

 

 

 

Expected number of white eye males _____    Expected number of wild type males _____
Expected number of white eye females ____    Expected number of wild type females _____

2) Create a new experiment, title it TASK 4. Set up the parent generation from your fly-file to cross a red-eyed male and a white-eyed female.

Actual number of white eye males ______    Actual  number of wild type males _____
Actual number of white eye females _____   Actual number of wild type females ____

3) Create a new experiment, title it TASK 4. Set up the parent generation from your fly-file to cross a white-eyed male and a red-eyed female.

Actual number of white eye males ______    Actual  number of wild type males _____
Actual number of white eye females _____   Actual number of wild type females ____

4) From the offspring in #3, do a back cross with one of the female offspring and the white-eyed male father. What do you EXPECT the ratio of the next generation offspring to be?

Actual number of white eye males ______    Actual  number of wild type males _____
Actual number of white eye females _____   Actual number of wild type females ____

Perform a chi-square analysis to show that your expected ratio matches the actual ratio.

What is your Chi-square sum?______ What is the Critical Value? _____ Is this a good fit or a poor fit? _______

5.  A researcher wants to create a stock of fruit flies where they can easily be identified as male or female based on the color of their eyes.   What Parental (P) genotypes would you need to be able to sex the flies by eye color.   Explain your choice using a Punnett square.

 

 

Task 5 - Determine the Genotype of an Unknown Fly

You receive a vial with fruit flies that an absent-minded intern forgot to label. You are given the following clues from the intern:

Go to the simulator and create a new experiment that includes the TASK5-Unknown flies. Your job is to determine the genotype of the flies, you can use any of the other flies in the fly-file to do this if you like or even design a new fly with the editor. You may also run multiple experiments, it might even be necessary if your initial experiment fails to provide useful results. Don't give up!

What is the genotype of the flies? Describe the experiment you used to determine the unknown genotype and how a chi square analysis could support your hypothesis.

 

 

 

 

 

 

Task 6 - Summary

This was a basic tutorial showing some of the genetics we have learned in class.  We will be returning to drosophilab to do experiments with linkage groups later.  

Write a reflection paper that answers the following question.    “How does drosophiLAB simulate inheritance patterns found in drosophila melanogaster?” This analysis should be approximately 1 page in length and include specific details from the tasks you completed in the virtual lab. Here are some words you might want to include in your analysis:

expected, observed, chi-square, parental, filial, monohybrid, punnett, ratio, wildtype, mutant, chromosome, drosophila, Mendel, generation, prediction, reciprocal cross, sex-linked

Rubric:

Overall demonstration of knowledge (Mendel's experiments, dihybrid and monohybrid crosses) ___3___2___1___0
Overall demonstration of knowledge (Sex- Linkage, chromosomal inheritance) ___3___2___1___0
Use of terms and attention to specific details: ___3___2___1___0