import re


def is_locus_valid(locus):
    """
    This function checks if locus is valid
    :param locus: string Input AGI
    :return: boolean. True if worked. False if format is not right.
    """
    if re.match(r"^AT[12345CM]G\d{5}$", locus, re.IGNORECASE):
        return True
    else:
        return False