def get_targetscan_ts_type(seed_length, nt1):
    """Returns the target site type according to TargetScan terminology."""
    ts_type = None
    if seed_length >= 7:
        if nt1 == 'A':
            ts_type = '8mer'
        else:
            ts_type = '7mer-m8'
    elif seed_length == 6:
        if nt1 == 'A':
            ts_type = '7mer-A1'
        else:
            ts_type = '6mer'
    return ts_type