def get_chrom_proportions(chrom):
    """Returns the proportion of every chromosome arms contribution to genome
    size."""
    total = 0
    for i in chrom:
        for j in chrom[i]['seq1']:
            if j != '-':
                total += 1
    prop = []
    for i in chrom:
        subtotal = 0
        for j in chrom[i]['seq1']:
            if j != '-':
                subtotal += 1
        prop.append(subtotal/total)
    return prop