Read mapping and mappability are different concepts: there is no straightforward relation between the number of times a read matches the genome and the mappability of the regions it maps to.

<p>Within an edit distance of 1 mismatch, the sequence IMG maps uniquely to location ING in the schematic genome “......PING-PONG.....”. However, the matched position is not unique in the genome, since considering 1 mismatch it has a frequency of 2 due to location ONG.