Add the number of QTLs found for a given marker.

    :arg marker, the marker we are looking for the QTL's.
    :arg qtls, the list of all QTLs found.

def add_qtl_to_marker(marker, qtls):
    """Add the number of QTLs found for a given marker.

    :arg marker, the marker we are looking for the QTL's.
    :arg qtls, the list of all QTLs found.

    """
    cnt = 0
    for qtl in qtls:
        if qtl[-1] == marker[0]:
            cnt = cnt + 1

    marker.append(str(cnt))
    return marker