This figure illustrates ΦX174 DNA sequenced with a longer primer (R4). Due to this, the primer had to be cleaved from the sequenced strand, and was done so by restriction enzymes.

 

Some disadvanges of longer primers include unsatisfactory expression of “C bands”. Due to splitting of the primer, the araC was less satisfactory, and the bands produced were either faint or not visible, and therefore ddCTP was used. Additionally, cutting difficulties can arise if there is more than one site for the restriction enzyme in the sequence.

 

A sequence of 120 nucletides from the restriction site can be read off, and the sequence agree’s with the published one. However, at position 4380 there is a disagreement with the published strand, however the trinucleotide b should be inserted between 4380-4381.