def primer_clean(primer):
    """Handle non-IUPAC entries in primers, maps I for inosine to N.

    >>> primer_clean("I")
    'N'

    Inosine is found naturally at the wobble position of tRNA, and can match
    any base. Structurally similar to guanine (G), it preferentially binds
    cytosine (C). It sometimes used in primer design (Ben-Dov et al, 2006),
    where degeneracy N would give similar results.
    """
    return primer.upper().replace("I", "N")