Explain why replication is called semiconservative.

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Detailed Solution

DNA replication is called semiconservative because in each new DNA molecule, one strand is from the original DNA and the other strand is newly synthesized.

What Happens in DNA Replication?

When a cell divides, it needs to copy its DNA so that each daughter cell gets the same genetic material. The double helix of DNA unwinds, and each strand serves as a template for building a new complementary strand.

Steps in Semiconservative Replication

Unwinding: DNA double helix is opened by enzymes like helicase.
Complementary Base Pairing: Free nucleotides pair with exposed bases (A with T, G with C).
New Strands Formation: DNA polymerase helps attach new nucleotides, forming two complete molecules.
Result: Each new DNA molecule has one old strand and one new strand.

Evidence

The Meselson-Stahl experiment proved this model in 1958. They showed that after replication, DNA molecules contained one old strand and one new strand, confirming the semiconservative theory.

Model	Description	Reality
Conservative	Original DNA stays intact, new DNA completely new	Not correct
Dispersive	Old and new DNA mixed randomly	Not correct
Semiconservative	One old strand, one new strand	Correct

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