What is the purpose of error-correcting codes in DNA-based data storage?

• A. They add redundancy so that original data can be recovered even when some retrieved sequences contain errors.
• B. They speed up data retrieval by bypassing errors.
• C. They reduce data size through compression.
• D. They replace incorrect sequences with guesses.

Answer: (A)

Error-correcting codes in DNA data storage work by adding extra, structured redundancy to the encoded data so you can recover the original information even when some retrieved DNA sequences contain errors. In practice, when DNA is synthesized and later sequenced, mistakes happen—substitutions, insertions, deletions, or missing reads. The redundancy built into the data creates relationships among bits or blocks that decoding can use to detect where something went wrong and correct it, sometimes by combining many reads to infer the most likely original sequence. This lets you reconstruct the full file despite imperfect reads.

The other ideas don’t fit as well: adding redundancy for correction doesn’t necessarily speed up retrieval; compression aims to shrink data, not to fix errors; and replacing incorrect sequences with guesses isn’t how error-correcting codes operate—correct decoding uses the redundancy to identify and fix errors rather than making arbitrary guesses.