Genetic 342 A&B Kenneth G Wilson Professory of Botany

Proof of Crossing Over to Explain Linkage

Harriet B. Creighton and Barbara McClintock 1931. working with corn and Curtis Stern simultaneously proove that Crossing over it the reciprocal exchange of chromatids. It is clear from history that Creighton and McClintock were first but their proff was less well knownuntil B. McClintock won the McArthur and the Nobel Prize. We will consider the Creighton-McClintock paper rather than Stern to avoid too much Drosophila genetics. The key to the proof involves finding a double heteromorphic chromosome for study. In corn there was the case of chromosome-9 with a knob on one end and a translocated piece from another chromosome added to the end.

Results of Cross

This is our friend Oliver the parrotlet, Oliver is a true parrot, the smallest in the world.