1. A system for sequencing a nucleic acid, comprising: a substrate comprising multiple sites that are configurable to sequence a plurality of different nucleic acids of different sequences in parallel; a circuit configured to receive data indicative of quality at the multiple sites; and a circuit configured to include a subset of the multiple sites for obtaining sequencing data based on the data indicative of quality and to exclude a subset of the multiple sites for obtaining sequencing data based on the data indicative of quality.