def translate_rna(rna):
    """Translate an RNA sequence to an amino acid sequence."""
    if type(rna) is list:
        rna = string.join(rna, '')
    length = len(rna)
    pos = 0
    protein = []
    while (pos < (length-2)):
        aa = translate_codon(rna[pos:pos+3])
        protein.append(aa)
        pos = pos + 3
    return string.join(protein, '')