In the following crosses, you should decide how the trait is inherited. Is it autosomal dominant, autosomal recessive, sex-linked dominant, or sex-linked recessive?  If two genes are being studied, are they linked or do they assort independently?  In each case, you should test your hypothesis against the observed results by performing  a Chi Square analysis of the data. If the Level of Significance is above 0.05, you should accept your hypothesis as being supported by the data. Always collect 10,000 offspring, unless you are told otherwise.

1. Cross a wild type female with a sepia eyed male. What is/are the phenotype(s) of the  F1 flies?   What is your predicted phenotypic ratio (hypothesis) for the F2 generation?  What are the observed results (F1  x  F1)?  Are there any differences between the sexes in the results of either the F1  or the F2?
 
 
 
 
 
 
 
 

What does the Chi Square test for significance tell you about your hypothesis?
 

Re-run the cross, but with the 100 sample size selected.
 

How does the Level of Significance differ when you use 100 versus 10,000 flies?
How do you account for the difference?

            Level of significance for 100 offspring = _______.
            Level of significance for 10,000 offspring = ______.

What is the pattern of inheritance for sepia? ________________________
 
 

2. Cross an ebony body female with a vestigial winged male (remember they each are wild-type for the other characteristics).  Then cross the F1’s to obtain the F2 generation.
What phenotypic ratio(s) do you predict for the F1 and F2? Are there any differences between the sexes in your results?  Perform a Chi Square analysis of your F2 results.
 
 

 Level of significance  = _____.  Is your hypothesis acceptable?

 Do the two genes in question assort independently or are they linked?

 What is the pattern of inheritance for ebony body and vestigial wings?
             __________________________
 

3. Cross a brown eyed female with an ebony bodied male.  What is/are the phenotype(s) of the F1 offspring?  Is there any difference between the sexes in your results?  Then testcross an F1 female.
 
 

 What is the phenotype and genotype of your testcross parent?
 

 What phenotypic ratio do you predict for your testcross offspring?
 
 
 

 Was your hypothesis accepted?         Level of significance =  _______.

 Do the two genes assort independently or are they linked?

 Was your F1 female homozygous or heterozygous for each gene, based on your
            testcross results?

 What is the pattern of inheritance for brown eye and ebony body?
            _____________________
 
 
 

4. Cross a tan bodied female with a wild type male.  Describe the F1 phenotypes.
 

What is your hypothesis for the mode of inheritance of tan body?  Can you test your hypothesis by crossing an F1 female with an F1 male?  What would you predict from such a cross?
 
 
 
 
 
 

 Is your hypothesis supported by the data from an F1 female x  an F1 male?
 
 

 Level of significance = _____.
 

 What is the inheritance pattern for tan body?  ____________________
 

5.  Turn to page 265 in your textbook.  Let us see if we can reproduce the results that are presented in Figs. 15.4 and 15.5.

Cross a wild type female with a male that has black body and vestigial wings.  This will give you double heterozygotes.  Cross an F1 female (the female that is depicted in the upper left hand corner of Fig. 15.4 with  a male that has a black body and vestigial wings (the male on the right).  This is, of course, a testcross.

What are the phenotypes and numbers of the testcross progeny.
 
 

Calculate the recombination frequency  (see Fig. 15.5).  It is _____.  How does this compare with the 17% in Fig. 15.5?
 

6.  Cross an eyeless female with a male that has shaven bristles .  Describe the F1 flies, and predict the results of a testcross experiment.  Next, testcross  an F1 female, and describe the phenotypes (and numbers) of the offspring. Do you observe any sex differences in the testcross progeny?
 
 

Was your hypothesis accepted?         Level of significance  =  _______.
Did the two genes assort independently?  Explain.
 

 Explain the inheritance of eyeless and shaven bristles.
 
 
 
 
 

7. Cross a bar-eyed female with a wild type male.  Describe the phenotypes of the F1 offspring.  How can you explain this inheritance pattern?  What is your hypothesis?
Will it help if you include the F2 in your explanation?
 
 
 
 
 
 
 
 

Level of significance = _______.

 Bar eye is inherited as a _____________________.
 
 
 

8.  Cross a female with vestigial wings with a male that has white eyes. Describe the F1 flies and cross them to obtain F2 offspring.

Describe the F2 offspring.
 
 
 

Explain the inheritance of vestigial wings and white eyes. Give evidence for your hypothesis.
 
 
 
 
 
 

  Test your experimental results against your expected numbers.
  Level of significance = ______.
 

You are now finished.  Hand the answers in to your TA who will grade them.