DNA replication is said to be semiconservative because: One of the new molecules conserves both of the original DNA strands. The new DNA molecule contains two new DNA strands. Both of the new molecules contain one new strand and one old strand. DNA polymerase conserves both of the old strands.
The Correct Answer and Explanation is:
The correct answer is: Both of the new molecules contain one new strand and one old strand.
Explanation:
DNA replication is called semiconservative because, during the replication process, each of the two newly formed DNA molecules consists of one original (or “old”) strand and one newly synthesized strand. This concept was first demonstrated by the famous Meselson and Stahl experiment in 1958, which provided evidence for this mechanism.
Here’s how it works:
- Unwinding and Separation: The DNA molecule unwinds with the help of enzymes such as helicase, creating two single-stranded templates.
- Synthesis of New Strands: Each of these single-stranded templates serves as a guide for the formation of a complementary strand by DNA polymerase, an enzyme that catalyzes the addition of nucleotides according to base pairing rules (A with T, and C with G). These new strands are created in the 5′ to 3′ direction.
- Final Result: After replication, there are two double-stranded DNA molecules. Each molecule has one strand that is derived from the original DNA (the parent strand) and one strand that is newly synthesized (the daughter strand). This is why the process is called semiconservative—half of the original DNA is “conserved” in each of the new DNA molecules.
This mechanism ensures that the genetic information is accurately passed down to daughter cells during cell division, maintaining the integrity of the genome. The term “conservative” could have been used if the entire original DNA molecule was conserved in one of the new molecules, but that’s not the case in semiconservative replication.
