Which statement best describes semiconservative replication?

• A. Both strands are copied anew with no parental template
• B. Only one strand is copied
• C. Each new DNA molecule contains one old strand and one newly synthesized strand
• D. Replication produces molecules with two new strands

Answer: (C)

Semiconservative replication means that each new DNA molecule contains one original (parental) strand and one newly synthesized strand. When the double helix unwinds, each parental strand serves as a template for building a complementary strand. DNA polymerase adds nucleotides to the growing strand in the 5′ to 3′ direction, producing two daughter molecules that each retain one old strand and one new strand. This explains why the correct description is that every new molecule has one old and one newly synthesized strand. The other ideas—copying both strands anew without a template, copying only one strand, or producing two entirely new strands—don’t reflect how parental information is preserved during replication.