Can the oligos without additional modification be used in allelic specific PCR?
You can use unmodified oligos in allelic specific PCR. You would want to place the allele directly on the 3' end of your primer. If the wt base is present, the full primer will hybridize and you will get extension. If the mutant base is present, the 3' base will not hybridize and you shouldn't see amplification. You can do and endpoint assay by running the product on a gel to see if you had any amplification or you can use Sybr green to monitor the amplification.