Why is sequencing of a cloned insert important after plasmid construction?

• A. To determine if the plasmid is circular
• B. To confirm the insert sequence matches the design and to verify correct junctions and absence of mutations
• C. To measure plasmid copy number
• D. To assess protein expression

Answer: (B)

Verifying the exact nucleotide sequence of the cloned insert and its junctions with the vector is essential to ensure the construct matches the intended design. Sequencing confirms that the insert is present, in the correct orientation, and free of mutations that could alter the encoded protein or disrupt reading frames and regulatory elements. It provides definitive evidence that the assembly worked as planned, so downstream experiments like expression or functional studies are based on a correct construct. This step isn’t about circularity, copy number, or measuring protein expression, which rely on other methods; sequencing specifically validates the genetic sequence and junction integrity to prevent costly misinterpretations later.