Question about primer design

Hi r/biology, can someone explain to me how to go about designing a primer to detect a polymorphic region of a gene? If the polymorphic region is represented as a Y (unknown), what nucleotide would one use that would be complementary to it when the Y is unknown? For example this sequence: 5' gtagccacag tcagtggaac aagcccagta agccaaaaac caacaygaag catgtggcag3' how would you go about designing a complementary primer for this? Thanks.