FlyLab Exercise 5
Biological Sciences 355
Honors Genetics
Virtual FlyLab Exercise 5
Complete these experiments before recitation on Fri., Oct. 17.
Data to be e-mailed by Wednesday, Oct. 17 at 4 PM
In Exercise 3, you mapped the recessive markers ebony body (e), spineless bristle (ss), sepia eye (se)
and incomplete wing-vein (ri) by a series of two-point crosses in cis.
In this exercise, you will map the same genes by a series of 3-point crosses. The procedure you will
use differs slightly from that we used in class to accommodate the peculiarities of
Drosophila melanogaster and the current limitations of the Virtual FlyLab server.
Experiments:
1. Cross e, ss, se 
x wt 
; cross F1 x P .
2. Cross e, ss, ri x wt ; cross F1 x P .
3. Cross ss, se, ri x wt ; cross F1 x P .
4. Cross e, ri, se x wt ; cross F1 x P .
For each experiment:
a) Identify the single-crossover and double-crossover classes
b) Calculate the recombination frequency between each pair of markers.
c) Draw a genetic map of the three markers including distances
Finally:
a) Draw a genetic map most consistent with your combined data from all four experiments,
showing gene order and map distances.
On or before Wednesday, Oct. 15 at 4 PM, Send a copy to of your map to the instructor by e-mail to
ljac@pitt.edu
in the form
marker1--distance--marker2--distance--marker3--distance--marker4
b) Note any significant inconsistencies between the various experiments.
Can you propose an explanation for any such inconsistencies?
c) Compare your final map to the one you obtained by two-point crosses in exercise 3.
If you have trouble with the Virtual FlyLab,
please consult Dr. Jacobson in person, by telephone or by e-mail.
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This information was prepared for Fall Term 2008. Report broken links or comments to:
Dr. Lewis Jacobson
Copyright © 1995-2008, Lewis Jacobson