Download Fruit Fly Genetics

LAB: Virtual Fruit Fly
Name
Question: Given phenotype information from a series of genetic crosses, how could you determine the
genotypes of the parents and mode of inheritance? Can you confirm your predicted genotypes and mode of
inheritance using a statistical analysis?
The common fruit fly is a model organism for genetic studies. The reason it is so widely used is because it is
easily cultured in the lab, has a short generation time, and can produce many offspring.
Determining the Mode of Inheritance in a Cross and Parental Genotypes
In order to determine the genotypes of parents, we must look at the ratios of phenotypes of the offspring. In this
virtual activity, you will mate fruit flies with certain traits and then analyze the products of that mating under a
microscope for the different phenotypes in subsequent generations (the data of which you will record). Each cross
produces a new generation two weeks later. Recall that there must be a P (parental) generation before you can have a
F1 generation. The idea here is to work back to the parental genotypes from the ratios of the F 1 and F2 phenotypes
you get from your crosses. This requires a bit of detective work, since there are several possible parental crosses.
In fruit fly genetics, the normal fly is called a "wild type" and any fly exhibiting a phenotypic mutation is called a
"mutant". Mutant flies are given names that generally denote the type of mutation the fly exhibits.
Directions:
1. Go to Fly Genetics: http://www.sciencecourseware.org/vcise/drosophila/ and enter as a guest.
2. Click on the computer to order flies.
3. Determine what flies you need based on the cross you will perform and add to cart.
4. View shopping cart (make sure they are the ones you need!) and check out.
5. Follow the steps to mate your flies (help usually will show up in yellow boxes).
6. Once mating is complete, follow the steps to analyze them under the microscope. Sort flies and record
data from the cross in the data table below. (You may need to hover over the pile of flies to know their
phenotype).
7. Click on a pile of flies to view an individual fly closely. You’ll use one of these in a new mating (click
Use in New Mating and then zoom out). Repeat this step with the other pile of flies.
8. Return to lab to complete that mating, and then analyze your F2 results. Record data.
9. As you look at your numbers, think about what mode of inheritance (autosomal dominant, autosomal
recessive, X-linked recessive, etc) was used and write a null hypothesis. Remember, for genetics
probability problems, the null hypothesis states that there is no difference between the observed data
and the data expected for the cross you predict.
10. Complete all follow up questions for this cross.
11. Return to lab and order flies for the next cross.
Cross 1: Wild Type Female x Vestigial Winged Male
PHENOTYPE
Wild Type Males
Vestigial Winged Males
Wild Type Females
Vestigial Winged Females
Predicted Genotypes:
F1 Generation
x
F2 Generation
Write a NULL hypothesis that describes the mode of inheritance for the trait(s) you studied:
There is no difference between the observed data and the data expected for a(n)
cross.
I would expect this pattern/ratio in the F1 offspring:
I would expect this pattern/ratio in the F2 offspring:
Are the deviations for the phenotypic ratio of the F2 generation within the limits expected by chance?
To answer this question, statistically analyze the data using the Chi-square analysis. Calculate the Chi-square statistic for
the F2 generation in the chart below.
Phenotypes
Observed (o)
Expected (e)
(o-e)
(o-e)2
(o-e)2 / e
X2 =
Degrees of Freedom:
Refer to the critical values chart. What is the probability (p) value for these data?
What is the significance?
Remember: The minimum value for rejecting the null hypothesis in the sciences is 0.05. This means that only 5% of the time would you expect to see
similar data if the null hypothesis is correct OR you are 95% sure the data does not fit the expected ratio.
If the calculated X2 value is greater than or equal to the critical value from the table, then the null hypothesis is REJECTED.
According to the probability (p) value, can you accept or reject your null hypothesis for this cross? Explain.
What are the genotypes of the P1 flies? FEMALE ________________ MALE _______________
What are the genotypes of the F1 flies? FEMALE ________________ MALE _______________
Is the mutation (trait of interest) autosomal or sex-linked? ______________
Is the mutation dominant or recessive? _______________
Mode of Inheritance:
Is this F1 cross a monohybrid or dihybrid cross? __________________
In the space below, make 2 (small!) Punnett squares showing parents and F1 and F2 offspring for this trait.
Cross 2: White Eyed Female x Wild Type Male
PHENOTYPE
Wild Type Males
White eyed Males
Wild Type Females
White eyed Females
Predicted Genotypes:
F1 Generation
x
F2 Generation
Write a NULL hypothesis that describes the mode of inheritance for the trait(s) you studied:
There is no difference between the observed data and the data expected for a(n)
cross.
I would expect this pattern/ratio in the F1 offspring:
I would expect this pattern/ratio in the F2 offspring:
Are the deviations for the phenotypic ratio of the F2 generation within the limits expected by chance?
To answer this question, statistically analyze the data using the Chi-square analysis. Calculate the Chi-square statistic for
the F2 generation in the chart below.
Phenotypes
Observed (o)
Expected (e)
(o-e)
(o-e)2
(o-e)2 / e
X2 =
Degrees of Freedom:
Refer to the critical values chart. What is the probability (p) value for these data? _______________
What is the significance?
Remember: The minimum value for rejecting the null hypothesis in the sciences is 0.05. This means that only 5% of the time would you expect to see similar data if
the null hypothesis is correct OR you are 95% sure the data does not fit the expected ratio.
If the calculated X2 value is greater than or equal to the critical value from the table, then the null hypothesis is REJECTED.
According to the probability (p) value, can you accept or reject your null hypothesis for this cross? Explain.
What are the genotypes of the P1 flies? FEMALE ________________ MALE _______________
What are the genotypes of the F1 flies? FEMALE ________________ MALE _______________
Is the mutation (trait of interest) autosomal or sex-linked? ______________
Is the mutation dominant or recessive? _______________
Mode of Inheritance:
Is this F1 cross a monohybrid or dihybrid cross? __________________
In the space below, make 2 (small!) Punnett squares showing parents and F1 and F2 offspring for this trait.
Cross 3: Wild Type Female x Sepia Eyed, Vestigial Winged Male
PHENOTYPE
Predicted Genotypes:
F1 Generation
x
F2 Generation
Wild Type Males
Wild Type Female
Total Wild Types
Vestigial Winged Males (normal eyes)
Vestigial Winged Females (normal eyes)
Total Vestigial Winged (normal eyes)
Sepia eyed Males (normal wings)
Sepia eyed Females (normal wings)
Total Sepia eyed (normal wings)
Vestigial Wings, Sepia eyed Males
Vestigial Wings, Sepia eyed Females
Total Vestigial Wings, Sepia eyed
Write a NULL hypothesis that describes the mode of inheritance for the trait(s) you studied:
There is no difference between the observed data and the data expected for a(n)
cross.
I would expect this pattern/ratio in the F1 offspring:
I would expect this pattern/ratio in the F2 offspring:
Are the deviations for the phenotypic ratio of the F2 generation within the limits expected by chance?
To answer this question, statistically analyze the data using the Chi-square analysis. Calculate the Chi-square statistic for
the F2 generation in the chart below.
Phenotypes
Observed (o)
Expected (e)
(o-e)
(o-e)2
(o-e)2 / e
X2 =
Degrees of Freedom:
Refer to the critical values chart. What is the probability (p) value for these data? _______________
What is the significance?
Remember: The minimum value for rejecting the null hypothesis in the sciences is 0.05. This means that only 5% of the time
would you expect to see similar data if the null hypothesis is correct OR you are 95% sure the data does not fit the expected ratio.
If the calculated X2 value is greater than or equal to the critical value from the table, then the null hypothesis is REJECTED.
According to the probability (p) value, can you accept or reject your null hypothesis for this cross? Explain.
What are the genotypes of the P1 flies ? FEMALE ________________
What are the genotypes of the F1 flies? FEMALE ________________
MALE _______________
MALE _______________
Is the mutation (trait of interest) autosomal or sex-linked? ______________
Is the mutation dominant or recessive? _______________
Mode of Inheritance:
Is this F1 cross a monohybrid or dihybrid cross? __________________
In the space below, make 2 (large!) Punnett squares showing parents and F1 and F2 offspring for this trait.
P1 cross:
F1 Cross:
Cross 4: Wild Type Female x Sepia Eyed, Ebony body Male Predicted Genotypes:
PHENOTYPE
F1 Generation
x
F2 Generation
Wild Type Males
Wild Type Female
Total Wild Types
Ebony body Males (normal eyes)
Ebony body Females (normal eyes)
Total Ebony body (normal eyes)
Sepia eyed Males (normal wings)
Sepia eyed Females (normal wings)
Total Sepia eyed (normal wings)
Ebony body Sepia eyed Males
Ebony body, Sepia eyed Females
Total Ebony body, Sepia eyed
Write a NULL hypothesis that describes the mode of inheritance for the trait(s) you studied:
There is no difference between the observed data and the data expected for a(n)
cross.
I would expect this pattern/ratio in the F1 offspring:
I would expect this pattern/ratio in the F2 offspring:
Are the deviations for the phenotypic ratio of the F2 generation within the limits expected by chance?
To answer this question, statistically analyze the data using the Chi-square analysis. Calculate the Chi-square statistic for
the F2 generation in the chart below.
Phenotypes
Observed (o)
Expected (e)
(o-e)
(o-e)2
(o-e)2 / e
X2 =
Degrees of Freedom:
Refer to the critical values chart. What is the probability (p) value for these data? _______________
What is the significance?
Remember: The minimum value for rejecting the null hypothesis in the sciences is 0.05. This means that only 5% of the time
would you expect to see similar data if the null hypothesis is correct OR you are 95% sure the data does not fit the expected ratio.
If the calculated X2 value is greater than or equal to the critical value from the table, then the null hypothesis is REJECTED.
According to the probability (p) value, can you accept or reject your null hypothesis for this cross? Explain.
What are the genotypes of the P1 flies ? FEMALE ________________
What are the genotypes of the F1 flies? FEMALE ________________
MALE _______________
MALE _______________
Is the mutation (trait of interest) autosomal or sex-linked? ______________
Is the mutation dominant or recessive? _______________
Mode of Inheritance:
Is this F1 cross a monohybrid or dihybrid cross? __________________
In the space below, make 2 (large!) Punnett squares showing parents and F1 and F2 offspring for this trait.
P1 cross:
F1 Cross: