Why does one combine PCR and cloning as ways for amplification of sequences? Don't they produce the same result? I was reading the paper https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1864885/ and got confused by the following passage:
Cloning and Bisulfite Genomic Sequencing
Each bisulfite-converted DNA sample was subjected to PCR by primers that did not discriminate between methylated and unmethylated sequences, using a GeneAmp PCR core reagent kit (Applied Biosystems). The primer sequences are listed in Table 1, and reaction conditions are listed in Supplemental Tables 1C and 1D (available online at http://ajp.amjpathol.org). Each subsequent PCR product was TA-cloned into pGEM-Teasy vector25 (Promega) for transformation into Escherichia coli strain JM109, according to the manufacturer’s instructions. Clones were picked randomly and colony PCR was then performed using vector primers T7 and SP6 to amplify the cloned inserts. Cycle sequencing was performed using BigDye version 1.1 (Applied Biosystems) and an automated capillary DNA sequencer Genetic Analyzer 3100 (Applied Biosystems). The sequences obtained were aligned and compared using SeqScape software (Applied Biosystems). The completeness of bisulfite conversion was first confirmed before scoring. The CpG sites sequenced as cytosine or thymine residues were scored as methylated or unmethylated, respectively. The methylated site frequency was calculated for each sample by dividing the total number of methylated sites over all cloned CpG sites.
Can someone comment on what purpose the cloning serves when the amplification is already done by PCR?