What Can Fruit Flies Reveal about Inheritance?

 

Lab Notebook

Chi-Square test for Case 1

 

Phenotype

 

Observed No. (o)

 

Expected No. (e)

 

(o–e)

 

(o–e) 2

 

 (o–e) 2

e

Red eyes

 

 

Sepia eyes

 

 

 

c2 (to the nearest ten-thousandth)

 

 

 

 

Questions

1. Why is it important to remove the adults in the parental generation?

2. What generation will their offspring be?

3. Based on the data obtained, is the cross in Case 1 monohybrid or dihybrid? Explain.

4. Is the cross in Case 1 sex–linked or autosomal? Explain.

5.  Based on the data obtained, is the most likely mode of inheritance in Case 2 autosomal or sex–linked? Explain.

6. From the data presented, what is the genotype of the parental (before the F1 generation; not shown here) generation?

7. Determine the degrees of freedom. This is the number of categories (red eyes or sepia eyes) minus one. For the data in Case 1, what is the number of degrees of freedom?

8. Find the probability (p) value for 1 degree of freedom in the 0.05 row. Compare this with the chi–square value you calculated in your Lab Notebook. What can you say about the null hypothesis?