Try redoing the chi-square test if you think that the observed numbers were very proximal to your expected numbers. You said that your value was 140, but if the observed-expected numbers were similar, the test would be taking the sum of numbers very close to zero and thus your chi-square value will be low, not high, which 140 is. 14 is pretty high. 1.4 is a value you can feel comfortable with. Double check your math, and if you still get a very large chi-square value, and p<.05, you have to start thinking about alternative hypotheses. Like I mentioned before, I think that in a general biology fruit fly lab, especially the first one, the profs. have the lab designed to make you reject your null hypothesis, which is normally a simple genetic system, and make you think about alternatives, just so you get accustomed to using the scientific method. Anyhow, double check your calculations and let us know what's going on.