You are setting up a PCR reaction and add a primer for one end of the target sequence, but you forget to add the primer for the other end of the target sequence. If you added the other necessary components, what do you expect to observe after running the PCR reaction for 40 cycles
If only one primer is added, it can still form a product, which is used in the sequencing reactions. The product formed will be only single stranded because of the presence of single primer.
