1. Genetics of Organisms
AP Lab 7

2. Far Side, Gary Larson…

3. Background
Drosophila melanogaster is a model organism used often in genetics experiments.
Why?
Short reproductive cycle
Produces large numbers of offspring
Small, easy to maintain
Easy to observe traits

4. Images of Drosophila

5. Mock lab
Since performing experiments with real flies will take too long, we will use mock data to complete the lab.
Assume our research was completed on the wild type- (red) versus white-eyed flies.
This is an example of sex-linked inheritance

6. The code
We will use the following shorthand to represent eye color alleles: XR
Wild-type X Xr
White X Y

7. White eyed is recessive
Some facts…
Female = XX
Male = XY
Wild-type is dominant
White eyed is recessive

8. Mock data P generation = Xr Xr x XRY Table 7.1 F1 Generation Data
Phenotype and symbol
Females
Males
Red eye
All XR Xr
White eye
All XrY

9. Mock data, part 2 F1 cross: XR Xr x XrY Phenotype and symbol Females
Red eye
78 XR Xr
69 XRY
White eye
62 Xr Xr
73 XrY

10. Analysis of Results Answer questions 1-6 in your lab packet. Remember…
Expected ratios are what you predict will happen based on probability and Punnett Squares
Observed ratios are what you actually get from mating the flies

11. Analysis of Results, part 2
Question 7: fill in the first 5 columns, and read ahead about Chi-Square. Then answer the three discussion questions.
Homework: Preview the Statistical Analysis section and fill in as much as you can. Write down any questions you have. This is where we will pick up next time.