  Owing to its longevity and enormous information density, DNA, the molecule
encoding biological information, has emerged as a promising archival storage
medium. However, due to technological constraints, data can only be written
onto many short DNA molecules that are stored in an unordered way, and can only
be read by sampling from this DNA pool. Moreover, imperfections in writing
(synthesis), reading (sequencing), storage, and handling of the DNA, in
particular amplification via PCR, lead to a loss of DNA molecules and induce
errors within the molecules. In order to design DNA storage systems, a
qualitative and quantitative understanding of the errors and the loss of
molecules is crucial. In this paper, we characterize those error probabilities
by analyzing data from our own experiments as well as from experiments of two
different groups. We find that errors within molecules are mainly due to
synthesis and sequencing, while imperfections in handling and storage lead to a
significant loss of sequences. The aim of our study is to help guide the design
of future DNA data storage systems by providing a quantitative and qualitative
understanding of the DNA data storage channel.
