How can random access be achieved in a DNA data storage system?

• A. By using PCR primer sets to selectively amplify targeted data blocks.
• B. By using unique address sequences and PCR primer sets to selectively amplify targeted data blocks.
• C. By indexing with color-coded tags.
• D. By sampling sequences randomly.

Answer: (B)

Random access is achieved by tagging each data block with a unique address and using PCR primers that flank that block to selectively amplify it from the mixed DNA pool. The address serves as a distinctive fingerprint so the primers bind only to the desired block, enriching it during amplification. This makes it possible to read just that specific block without sequencing everything in the storage pool. Without unique addresses, primers wouldn’t have a reliable target to differentiate one block from thousands of others, so targeted amplification wouldn’t be feasible. While other ideas like color-coded tags or random sampling might sound helpful, they don’t provide a reliable, scalable way to directly retrieve a chosen block; random sampling won’t guarantee access to the exact data you want.