Pre-adapter artifacts (in hybrid selection)
Various sources of error affect the hybrid selection (HS) process. Pre-adapter artifacts are those that arise in the preparation step(s) prior to the ligation of the PCR adapters. These artifacts occur on the original template strand, before the addition of adapters, so they correlate with read number orientation in a specific way.
A classic example is the shearing of target genomic DNA leading to oxidation of an amine of guanine at position 8 8-oxoguanine (8-OxoG, OxoG) (doi:10.1093/nar/gks1443) (see also OxoG entry in this dictionary).