How is DNA accurately replicated?

Scientists hypothesized three potential models on DNA replication

1. Conservative Mechanism - when replicated, the original strand of DNA remains the same while one identical copy is produced

2. Semi-Conservative Mechanism - when replicated, the two strands of DNA produced are half of the original DNA and half of the new DNA

3. Dispersive Mechanism - when replicated, the two strands of DNA are bits and pieces of the new and old strands of DNA

The correct model - Semi-Conservative Mechanism.

Why do we know?

• to test, they used a N15 isotope and took cell with DNA that is all N14 and let them grow in a medium containing only N15; all new DNA contains N15

• when taking the semi-conservative replicated strand and replicating it again the same way, the DNA contained both the N15 strand and the N14/N15 strand

Conclusion

• DNA is replicated through semi-conservative mechanisms, in which…

  • A) 2 strands are separated by breaking hydrogen bonds b/w A-T and C-G

  • B) 2 separated strands are used as a template to build new DNA