Which DNA strand is synthesized continuously?

• A. Leading strand
• B. Lagging strand
• C. Template strand
• D. Antisense strand

Answer: (A)

DNA polymerase can only add nucleotides in the 5' to 3' direction. The leading strand is oriented so that its template runs 3' to 5' toward the replication fork, allowing DNA polymerase to synthesize it continuously as the fork advances. The other strand runs 5' to 3' toward the fork, so synthesis must occur in short pieces (Okazaki fragments) separated by RNA primers, making that strand discontinuous. The terms template strand and antisense strand describe which strand serves as the template in different contexts, but they don’t define the mode of synthesis like the leading vs lagging distinction. So the strand synthesized continuously is the leading strand.