modified sub chr to return only one chromosome. corrected bug in sub get_chromosomes to return all chromosomes
modified sub chr to return only one chromosome. corrected bug in sub get_chromosomes to return all chromosomes

LyonsLab/coge,LyonsLab/coge,LyonsLab/coge,asherkhb/coge,LyonsLab/coge,LyonsLab/coge,LyonsLab/coge,asherkhb/coge,asherkhb/coge,asherkhb/coge,LyonsLab/coge,asherkhb/coge,LyonsLab/coge,asherkhb/coge,asherkhb/coge,LyonsLab/coge,asherkhb/coge,asherkhb/coge