Crossing over between the colorless (c) / colored (C) and starchy (Wx) / waxy (wx) endosperm traits in maize can be correlated with cytological markers: a knob at one end of the chromosome and a translocation at the other end.

For example, the colorless, waxy recombinant chromosome (case I) has lost its knob, providing visual evidence that physical exchange of genetic material had occurred.