Non-Mendelian ratios?

Question

What are the ways one would get non-Mendelian ratios?
Is it possible to do a Punnet square with two species?

Answer 1

There are many ways to get non-Mendelian ratios. These include codominance, incomplete dominance, and complementation, to name a few. A punnet square could be done with two species, but would not necessarily show anything worthwhile, as the gametes would most likely not be compatible.