def calc_disordered_regions(limits, seq):
    """
    Returns the sequence of disordered regions given a string of
    starts and ends of the regions and the sequence.
    
    Example
    -------
    limits = 1_5;8_10
    seq = AHSEDQNAAANTH...
    
    This will return `AHSED_AAA`
    """
    seq = seq.replace(' ', '')
    
    regions = [tuple(region.split('_')) for region 
               in limits.split(';')]
               
    return '_'.join([seq[int(i)-1:int(j)] for i,j in regions])