What is a major challenge associated with PCR amplification in DNA data storage?

• A. Amplification bias and sequence dropout can skew data representation and introduce errors; additional steps are needed to control bias.
• B. Amplification bias and sequence dropout can skew data representation.
• C. PCR completely eliminates biases.
• D. PCR only increases sequence length.

Answer: (B)

PCR amplification in DNA data storage is challenged mainly by amplification bias and sequence dropout, which distort how data is represented after reading it back. Different sequences don’t amplify equally well because of factors like primer binding efficiency, GC content, secondary structures, and sequence length. This means some data-carrying strands become highly overrepresented while others are underrepresented or lost entirely, so the recovered sequence pool no longer faithfully reflects the original data. In a storage system, that skew can lead to decoding errors unless bias is managed. That’s why it’s important to use strategies to control bias, such as optimizing amplification conditions, employing encoding schemes with error-correcting codes, and considering methods to normalize or mitigate uneven amplification. The other statements don’t fit because PCR does not eliminate biases, nor does it merely increase sequence length; it can introduce or exaggerate bias and doesn’t inherently guarantee uniform representation.