def find_start_codon(sequence):
    """Moves through a given sequence by threes until it finds 'AUG'.
    It will then slice off the start codon and return the sequence to be translated."""
    cond = 1
    none = []
    while cond == 1:
        codon = sequence[0:3]
        sequence = sequence[3:]
        #when it finds a start codon it cuts the codon and returns the remaining sequence
        if codon =='AUG':
            sequence = codon + sequence
            cond = 0
            return(sequence)
        #if the codon is not a start and there are fewer than three bases exits with empty list
        elif len(sequence) < 3:
            cond = 0
            return(none)
        else:
            pass