def call_alleles(call):
    """Return a list of the bases in each allele of the specified call.

    Parameters
    ----------
    call : pyvcf call
        Genotype call parsed by PyVCF.

    Returns
    -------
    alleles : list of str
        List of bases with one entry per allele.  For a diploid call, there will be a list of two strings.
        It is possible (and likely) there may be duplicate strings in the list.
    """
    if call.gt_bases is None:
        return ['.']
    alleles = call.gt_bases.split(call.gt_phase_char())
    return alleles
