Explain how a trait might seem to "disappear" for a generation, and then "reappear" in the following generation.

There are recessive and dominant genes. Dominant genes are genes that tend to "dominate" or stand out more and recessive genes are kind of "hidden" so to speak. If a grandmother has a dominant gene, but the grandfather has no gene like that at all, it will then become recessive with the next generation. However, if the next generation say it is a daughter, has children with a man that has that gene, but it is recessive as well, their children will have a 25% chance of having that gene dominantly.