Performing Drosophila Crosses

Preparing the Crosses

Collect virgin females with appropriate marker and put into a new vial.
Store the vials from which virgins are collected at 18° C when not using.
Store vials from which males are collected at room temperature.
Once 10 virgin females from a strain have been collected, add 4 males with the appropriate marker from a different strain.
Label the vial to indicate the cross type and generation (A1 = the first generation of the first cross).
Store the crosses in an appropriate temperature-controlled incubator.
After 5 days, flip the 14 flies into a new vial (there should be eggs visible at the surface of the food).
Label the new vial appropriately (A2 = the second generation of the first cross).
Repeat this cycle until enough progeny from the crosses have been produced.

The progeny from the crosses will start eclosing after ~10 days.
Record the date that the flies begin eclosing.
Once there are at least 20 flies in the vial, collect the progeny and sort according to phenotype.
Record the number of flies of each phenotype born.
Place the males and females into separate vials.
There should be 5 - 15 progeny flies in each vial.
- If necessary, separate/combine phenotypes (but not gender) to have an appropriate number of flies in the vial.
Label the vial with:

Keep the progeny vials in an appropriate incubator.
Repeat this process during the six days following the date of first eclosure.
- Wait to sort until there are at least 20 flies in the vial (usually 2 to 3 times per vial).
- Record the most likely date of birth before each sorting.
After six days, toss the vial.