Semiconservative DNA replication means that when DNA replicates, each of the two new DNA molecules produced contains one original (parental) strand and one newly synthesized strand. In other words, half of the original DNA molecule is conserved (kept) in each new DNA molecule, while the other half is newly made
. This mechanism was experimentally confirmed by the Meselson-Stahl experiment in 1958, which used isotopes of nitrogen to show that after one round of replication, DNA molecules are hybrids containing one old and one new strand. After subsequent rounds, a mixture of hybrid and fully new DNA molecules appeared, consistent with semiconservative replication
. The process involves the DNA double helix unwinding, with each strand serving as a template for the formation of a complementary new strand by base pairing. Enzymes like helicase unwind the DNA, and DNA polymerase synthesizes the new strands. This ensures genetic continuity, as each daughter DNA molecule retains one original strand, preserving the genetic information through cell divisions
. In summary:
- DNA replication produces two DNA molecules.
- Each new molecule has one original strand and one new strand.
- This conserves half of the original DNA in each new molecule.
- The process maintains genetic continuity across generations of cells.
This is why the replication is called "semiconservative" - "semi" meaning half, and "conservative" meaning preserving half of the original molecule
