anchor.diff:  					positions: positionData.join(" ")},
   					function(pdbData) {
   						// init view with the sequence and pdb data
  -						init(sequence, pdbData);
  +						init(sequenceData, pdbData);
   				});
   			};
   
   			// get sequence data & pdb data for the current gene & init view
  -			$.getJSON("getPfamSequence.json", {geneSymbol: gene}, getPdbData);
  +			if (self.options.mut3dVis)
  +			{
  +				$.getJSON("getPfamSequence.json", {geneSymbol: gene}, getPdbData);
  +			}
  +			else
  +			{
  +				// if no 3D visualizer is available, just skip pdb data retrieval
  +				$.getJSON("getPfamSequence.json", {geneSymbol: gene}, init);
  +			}
   		},
   		/**
   		 * Initializes the mutation diagram view.
  
positive.code: 			var getPdbData = function(sequenceData)
  			{
  				// TODO sequenceData may be null for unknown genes...
  
  				// get the first sequence from the response
  				var sequence = sequenceData[0];
  
  
negative.code: 					// init diagram toolbar
  					mainView.initToolbar(diagram, gene);
  
  					if (self.mut3dVisView &&
  						pdbData)
  					{
  						// collection of pdb model instances
  						var pdbColl = self.util.processPdbData(gene, pdbData);
  
  						// init the 3d view
  						var view3d = new Mutation3dView({
  							el: "#mutation_3d_" + gene,
  