Process of Science

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 |31 |33 |2 |4 |.1212 |
|Sepia eyes |13 |11 |2 |4 |.3636 |

| |.4848 |
|(2 (to the nearest ten-thousandth) | |

Questions

1. Why is it important to remove the adults in the parental generation?
Its important to separate so one knows that F1 flies aer being crossed.

2. What generation will their offspring be?
F2 generation is the new offspring

3. Based on the data obtained, is the cross in Case 1 monohybrid or dihybrid? Explain.
Since there is only one trait (eye color) the cross is monohybrid which also shows a 3 to 1 ratio. If it was showing in a dihybrid it would have been 9:3:3:1ratio.

4. Is the cross in Case 1 sex–linked or autosomal? Explain.
The patterns seem the same for female and male so the cross is autosomal.

5. Based on the data obtained, is the most likely mode of inheritance in Case 2 autosomal or sex–linked? Explain.
There is a connection between the sex links…because no females had white eye so this shows a linkage between sex

6. From the data presented, what is the genotype of the parental (before the F1 generation; not shown here) generation?
X+XandX+Y
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?
There are 2 category minus 1…the degree of freedom is 1

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?