Question

why can a characteristic "jump" a generation?

Answer 1

Because of Mendel's First Law
http://www.ndsu.edu/pubweb/~mcclean/plsc431/mendel/mendel1.htm

What is seen in the F1 generation? We always see only one of the two parental phenotypes in this generation. But the F1 possesses the information needed to produce both parental phenotypes in the following generation. The F2 generation always produced a 3:1 ratio where the dominant trait is present three times as often as the recessive trait. Mendel coined two terms to describe the relationship of the two phenotypes based on the F1 and F2 phenotypes.