Which model describes how DNA replication occurs?

Which model describes how DNA replication occurs?

• A. Semiconservative model
• B. Conservative model
• C. Dispersive model
• D. Random model

Answer: (A)

DNA replication preserves genetic information by copying each strand while keeping the original strand as a template. In the semiconservative model, every new double helix is made of one old (parental) strand and one newly synthesized strand. The cell separates the two original strands and uses each as a guide to build a complementary new strand, so both daughter molecules end up with one old and one new strand. This pattern aligns with classic experimental results showing that after one round of replication, DNA molecules appear with intermediate density (one old and one new strand), and after a second round, the distribution matches continuing with one old strand in some molecules and only new strands in others. The alternative models would predict either two entirely new and entirely old molecules after the first round or a random mix of old and new segments within each molecule, neither of which matches those observed outcomes.

DNA replication preserves genetic information by copying each strand while keeping the original strand as a template. In the semiconservative model, every new double helix is made of one old (parental) strand and one newly synthesized strand. The cell separates the two original strands and uses each as a guide to build a complementary new strand, so both daughter molecules end up with one old and one new strand.

This pattern aligns with classic experimental results showing that after one round of replication, DNA molecules appear with intermediate density (one old and one new strand), and after a second round, the distribution matches continuing with one old strand in some molecules and only new strands in others. The alternative models would predict either two entirely new and entirely old molecules after the first round or a random mix of old and new segments within each molecule, neither of which matches those observed outcomes.