In PCR to sequencing that I do, the forward and reverse PCR primers each have a unique upfront tag sequence. Then the DNA is amplified with these primers and the PCR product contains both these unique tags in the product. In sequencing, the M13 universal F/R primers are used for sequencing which have just the same sequence as each of the upfront PCR tag. I then do bidirectional sequencing.
Now say that the forward PCR primer tag changed but reverse PCR primer tag stayed the same. The PCR product will contain the new forward primer tag in its product. For sequencing, I will only be able to sequence the reverse direction, is this right? Or will I not be able to sequence in either direction due to the one tag change in one of the PCR primers?