Students use a computer simulation, the commercial Biolabs Virtual Fly simulation, of fruit fly crosses to investigate the inheritance of a simple Mendelian trait. Students observe the results of initial crosses, make hypotheses about the inheritance of the trait, design crosses to test their hypothesis, analyze the results of their experiment and draw conclusions about the inheritance. This experiment uses a trait with simple dominant and recessive alleles appropriate for any beginning genetics students. A detailed example of how to do the crosses and a sample of a report along with a possible grading rubric are included. This excercise can be easily modified to include dominant, lethal or x-linked alleles.