Question

Describe the semi-conservative method of DNA replication with suitable diagrams.

Hint:

In semi-conservative replication, each new DNA molecule consists of one parent strand and one newly synthesized strand, ensuring the accuracy of the replication process.

Answer 1

Step 1: Definition of Semi-Conservative DNA Replication.
The semi-conservative method of DNA replication is a process by which DNA is copied, producing two identical DNA molecules. Each molecule consists of one original (parental) strand and one newly synthesized strand. This method was first proposed by Watson and Crick and later confirmed by the Meselson-Stahl experiment in 1958.
Step 2: Process of Semi-Conservative DNA Replication.
The process of semi-conservative DNA replication involves the following steps: - Step 2.1: Unwinding of the DNA double helix. The enzyme helicase unwinds the DNA at the origin of replication, creating a replication fork. The two strands of the DNA double helix separate, forming single-stranded templates. - Step 2.2: Primer binding. An RNA primer is synthesized by the enzyme primase. The primer provides a 3' hydroxyl group to which new nucleotides can be added. - Step 2.3: Elongation. DNA polymerase adds complementary nucleotides (A pairs with T, C pairs with G) to the growing strand, using the original strand as a template. The leading strand is synthesized continuously, while the lagging strand is synthesized in short fragments (Okazaki fragments). - Step 2.4: Removal of primers and filling gaps. The RNA primers are removed, and DNA polymerase fills in the gaps with DNA nucleotides. DNA ligase seals the sugar-phosphate backbone, completing the replication process.
Step 3: Diagram of Semi-Conservative DNA Replication.
[Include diagram of DNA replication showing the parental strand and newly synthesized strands.]

Final Answer: \[ \boxed{\text{Semi-conservative DNA replication involves each strand of the original DNA molecule serving as a template for the synthesis of a new complementary strand.}} \]