SL

For every couple with a heterogenous phenotype (2 Aas) there's a 50% chance for each child to cary the recessive gene yet not express it. If the genotype of the parents is AA and Aa it's a 25% chance, for Aa and aa it's a 75% chance. Now as you move along the generations you can multiply the probabilities. If you start with grandparents of an Aa genotype, there's a 50% chance for each child to carry both alleles. If they marry someone with an Aa genotype, the probabilty for a being present yet still dormant is 0.5*0.5=0.25=25%. If their partner has got a heterogenous dominant genotype, the probability is 0.5*0.25=0.125=12.5% and so on. Haircolor is a tricky example, since it's not determined by a single gene, things get a little bit more tricky with that (http://en.wikipedia.org/wiki/Human_hair_color).

So you are specifically looking for a virus that is transmitted by bites? I doubt it would have the potential to cause a pandemic based on some practical issues. The rabies virus causes a severe and finally lethal inflammation of the brain, which would result in hallucinations and like symptoms, which might cause the person infected to try and bite others. This inflammation would siginficantly lower the chances of them successfully biting and infecting anyone around them (consider the temporary disability caused by diseases like tick-borne encephalitis if it isn't promptly treated). The virus you have in mind would have to cause severe aggression in the patient (for example by altering the limbic system) without damaging any other parts of the brain, which would be hard to achieve. Besides, after the first couple of cases would become publicly known and the source of infection is identified (It shouldn't be too hard even for a very nearsighted doctor to find the bitemarks), it's too easy to avoid infection for the disease to pose a serious threat. So even though I have no doubt that it wouldn't be too hard to cause a pandemic, "Zombie viruses" probably wouldn't be the the way to do that.

If you are just interested in the results and not in the actual process of protein folding, you might want to use external servers. Those are generally free of charge, but if you want to use them in class it might take a while to get the results (at least if all students request the results). For modeling the 3D-structure of proteins using comparative modeling you could use SWISS-MODEL ( http://swissmodel.expasy.org/ ). For secondary structure and transmembrane domain prediction alone, another tool to consider would be PSIPred ( http://bioinf.cs.ucl.ac.uk/psipred/psiform.html ). If you prefer consensus prediction using several different algorithms, another website you could try @NPS ( http://npsa-pbil.ibcp.fr/cgi-bin/npsa_automat.pl?page=/NPSA/npsa_seccons.html ). For viewing the structures I'd use RASMOL, it has all the basic functionality you need and also doesn't cost anything ( http://rasmol.org/ ).