What is the molecular outcome of semi-conservative DNA replication in cells?

Introduction / Context:
Since the Meselson–Stahl experiment, it is established that DNA replication is semi-conservative. Each daughter duplex contains one parental strand and one nascent strand. This question confirms that core principle of molecular biology.

Given Data / Assumptions:

• DNA double helix consists of two antiparallel strands.
• Replication duplicates the genome prior to cell division.
• Base pairing rules guide accurate copying.

Concept / Approach:
Helicases unwind DNA; primase makes RNA primers; DNA polymerases extend in the 5′→3′ direction; and ligase seals nicks. Template-directed synthesis means each parental strand serves as a template for a new complementary strand, yielding two hybrid molecules that each contain one old and one new strand.

Step-by-Step Solution:
Parental duplex separates into two templates.DNA polymerase synthesizes complementary strands on both templates.Leading strand is continuous; lagging strand is discontinuous (Okazaki fragments).RNA primers are removed and gaps filled; ligase seals remaining nicks.End result: two daughter DNA molecules, each hybrid old/new.

Verification / Alternative check:
Meselson–Stahl used density-labeled nitrogen (15N to 14N shift) and CsCl gradients to show hybrid densities after one replication round, consistent only with semi-conservative replication.

Why Other Options Are Wrong:
Two completely new DNA molecules: would imply conservative replication, which is false.One new DNA and one old unchanged: also conservative model, disproven.One new RNA molecule: RNA is not the replication product of DNA; that is transcription.

Common Pitfalls:
Confusing conservative, semi-conservative, and dispersive models; assuming both strands are new after replication.

Final Answer:
Two DNA molecules such that each contains one original (parental) and one newly synthesized strand