fillInUI ( self,  parent )

intended layout: for multi-residue sequence lay out a label widget naming the chain (blank ID == "Principal Chain") and a text widget with that sequence. See gnats comments by Tom Goddard. Should be a status area so that the residue ID under the cursor can be reported in realtime. Also, a check button for connecting/disconnecting to graphics selection (default on). Put a status widget next to each chain label. If more than 5 chains, layout in multiple columns? Put the whole shebang (except status area) in a scrolled frame.