Today's lab will involve using the BioQUEST computer simulation program Genetics Construction Kit to determine how specific traits of virtual fruit flies are inherited.

PROCEDURES:

1. The contents of the hardrive can be viewed by double-clicking on the hardrive icon in the upper right corner of your Macintosh computer screen. A window will appear displaying the names of three folders: Applications, Documents, and System Folder.
2. Open the Applications folder by double-clicking on it.
3. Double-click the BioQUEST folder.
4. Double-click the Genetics Construction Kit folder.
5. Double-click the Genetics Construction Kit application icon (GCK ver. 1.03), and you should see the following:
   
   
   
   
6. Click anywhere on the BioQUEST logo to bring up the next screen:
   
   
   
   
7. Choose Monohybrid, Simple Dominance, click Start Problem, and Vial 1 containing a Field Population should appear:
   
   
   
   
   • The name of the trait (Thorax in this case) is presented in the rectangular box below and to the right of the name Vial 1.
   • This trait has two phenotypes listed in the box below the trait name (Bithorax and Grooveless in this example).
   • To the left of the phenotypes are four rows of male and female symbols corresponding to the number of males and females of each phenotype in the sample (the top two rows correspond to the first phenotype and the second two rows correspond to the second phenotype.
   • To view all of the individuals, align the cursor over the black rectangle below the vertical line separating the phenotypes from the individuals (the cursor changes to a new icon with arrows radiating in opposite directions from two parallel lines), depress the mouse button, and drag to the right.
   • The rectangular box directly above the male and female symbols has a small icon to the left which is a link to a notepad for that vial. You should type all pertinent information for this specific vial in this notepad (parental phenotypes, expected genotypes, results of statistical analysis, etc).
8. You must conduct a series of crosses to determine which trait is dominant and which is recessive.
9. Crosses are made by clicking on a male symbol, and while depressing the shift key clicking on a female symbol:
   
   
   
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   • Two individuals should now be highlighted.
   • Release the mouse button.
   • Pull down the Cross menu and select Cross Two.
10. A new window appears entitled Vial 2:
    
    • This vial contains the offspring of the cross you just made.
    • The offspring are represented by the male and female symbols in the left box.
    • The phenotypes of the offspring are represented by the names in the right box (remember that each phenotype corresponds to two rows of female and male symbols).
    • The information in the bottom of the box represents the parents: the number corresponds to the Vial number, the symbol represents the sex, and the name describes the phenotype.
    • If Vial 1 and Vial 2 are open, you can click on each parent in Vial 2 and observe that the same individuals are highlighted in Vial 1 (the program always keeps track of the parents).
    • Clicking in the open box in the left corner of the title bar closes the vial. Double clicking a closed vial opens it.
      
      
      
      
    • You can also view a summary of your data by choosing Summary Chart from the Analysis menu.
      
      
      
      
11. Statistical test of your results.
    • The next step in the process of determining how specific traits are inherited is to compare the results of your cross with expected results derived from a specific model of inheritance.
      • Monohybrid, Simple Dominance Model.
      • Monohybrid, Codominance Model.
      • Sex Linked Model.
      This is commonly done through use of a Goodness of Fit test such as a Chi squared test. Please note that a Chi squared test can't be performed if an expected value is zero.
    • To perform a Chi squared test, you must first activate the vial that contains the offspring to be tested: click in the center of the vial to activate it (the vial name should be highlighted).
    • Choose Chi Squared from the analysis tools menu.
      
      • A splash screen appears with the analysis.
      • By default all expected ratios are 1:1.
        
        
        
        
      • Adjust the expected ratio (if necessary). The values will be derived from your model of inheritance.
      • Highlight the cell adjacent to the phenotype in the Expected Ratio column and type in the correct value.
      • Click the Calculate button.
      • The analysis screen reports the P-value associated with this Chi squared value.
    
    
    
    
12. Record your notes in the notepad window.
    
    
    
    
13. Conduct additional crosses to determine which trait is dominant and which is recessive.
14. Additional information about using GCK can be obtained through reading the GCK Manual (in the same folder as the GCK program).
15. Construct a table of your results to include in your lab report.