This function will take the name of a data package and build a chromLocation object representing that data set. It has also been modified to allow further breakup of the chromLocs.
idiograb reads the position of the graphics pointer when the (first) mouse button is pressed. idiogram also reads a second position of the graphics pointer after another mouse button press. The two points selected are used to define a diagonal line from which a bounding box will be constructed. It then retrieves the gene identifiers of the points that lie within the bounding box.
providing 
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