Figure 8 from: Nilsson R, Tedersoo L, Abarenkov K, Ryberg M, Kristiansson E, Hartmann M, Schoch C, Nylander J, Bergsten J, Porter T, Jumpponen A, Vaishampayan P, Ovaskainen O, Hallenberg N, Bengtsson-Palme J, Eriksson K, Larsson K, Larsson E, Kõljalg U (2012) Five simple guidelines for establishing basic authenticity and reliability of newly generated fungal ITS sequences. MycoKeys 4: 37-63. https://doi.org/10.3897/mycokeys.4.3606

Figure 8 - Untrimmed sequences tend to look like this when run through BLAST. Note how the first ca. 20 bp., and the last ca. 30 bp., of the query sequence (represented by the red bar with scale marks every 100 bp.) do not align to any of the BLAST hits. The use of different but closely situated primers may give a similar pattern, however, pointing at the need to also look at the BLAST alignments for start and end positions of the reference sequences.