function changeSubsetOptions(){
      var org = $('organism').value;
      if(org == 'mouse') options = ['all','Entire Mouse Genome','430-2','Affymetrix GeneChip® Mouse Genome 430 2.0 Array'];
      else options = ['all','Entire Human Genome','133-2','Human Genome U133 Plus 2.0 Array'];
      var el = $('subset');
      el.options.length = 0;
      for(i=0;i<options.length;i+=2)
        el.options[el.options.length] = new Option(options[i+1],options[i],false,false);
}