Last semester I posted an essay introducing inheritance, the idea of factors/alleles, how alleles are distributed into sex cells that combine with other sex cells to bring about a new generation. Looking back on this post, I think it would be a good idea to point to it from here and suggest that all my General Biology students read through it to ensure that they understand the basics of inheritance before we go on.
You can go directly to that post here or drop through the wormhole on the right.