allow subset of chromosomes to be loaded
allow subset of chromosomes to be loaded

ssadedin/seqr,ssadedin/seqr,macarthur-lab/xbrowse,macarthur-lab/xbrowse,macarthur-lab/seqr,ssadedin/seqr,macarthur-lab/seqr,ssadedin/seqr,macarthur-lab/seqr,macarthur-lab/xbrowse,macarthur-lab/xbrowse,macarthur-lab/xbrowse,macarthur-lab/seqr,macarthur-lab/seqr,ssadedin/seqr,macarthur-lab/xbrowse