def dict_domains_in_chromosomes(domains_list):
    """Given a list of domains (chr start end) return a dictionary of with chromosomes as keys and list of domains
    as values"""
    chromosomes = {}
    for i in domains_list:
        chrom = i[0]
        if chrom not in chromosomes.keys():
            chromosomes[chrom] = [(i[1], i[2])]
        else:
            chromosomes[chrom].append((i[1], i[2]))
    return chromosomes