The Question is from neet-botany molecular-basis-of-inheritance dna, and it was created by the author D VINOD

Question

In eukaryotic DNA replication, which of the following is NOT a function of topoisomerase?

D VINOD · Accepted Answer

## CORE INFORMATION
✓ **Answer**: D
## CONCEPT FRAMEWORK
 **Primary Concept**: DNA replication in eukaryotes and the roles of enzymes involved.
 **Related Topics**: DNA structure, supercoiling, RNA primers, DNA polymerase.
 **Prerequisites**: Basic understanding of DNA replication process and the functions of key enzymes.
## SOLUTION PATHWAY
**Given Information**:
The question asks to identify the function NOT performed by topoisomerase during eukaryotic DNA replication.
**Method & Steps**:
1. **Understanding Topoisomerase:** Topoisomerases are enzymes that manage the topological state of DNA.  They primarily work by relieving torsional stress and preventing supercoiling that arises during DNA unwinding. This unwinding is necessary for the replication machinery to access the DNA strands. They achieve this by creating temporary breaks in the DNA strands, allowing them to rotate around each other, and then resealing the breaks. They also help untangle intertwined DNA strands.
2. **Analyzing the options:**
    * **A. Relieving torsional stress:** This is a key function of topoisomerase.  As the DNA helix unwinds ahead of the replication fork, it creates positive supercoiling, which topoisomerase relieves.
    * **B. Preventing supercoiling:**  Topoisomerase directly prevents the overwinding (positive supercoiling) of DNA ahead of the replication fork and underwinding (negative supercoiling) behind it.
    * **C. Untangling DNA strands:** Topoisomerases can help resolve DNA tangles, ensuring smooth replication.
    * **D. Synthesizing RNA primers:** This is the function of primase, not topoisomerase. RNA primers are short RNA sequences that provide a starting point for DNA polymerase to begin DNA synthesis.
3. **Conclusion:**
    The only option that is NOT a function of topoisomerase is synthesizing RNA primers.  Therefore, the correct answer is D.
## OPTION ANALYSIS
A ✓: Topoisomerase's role in relieving torsional stress is crucial for DNA replication.
B ✓:  Topoisomerase actively prevents the formation of supercoils that would hinder replication.
C ✓: Topoisomerase contributes to untangling the DNA strands and facilitating replication.
D :x: RNA primer synthesis is the function of primase, not topoisomerase.
## LEARNING AIDS
 **Common Mistakes**:
  1. Confusing the roles of topoisomerase and other enzymes involved in replication (e.g., helicase, primase, DNA polymerase).
  To avoid this, make a table summarizing the functions of each key enzyme.
  2.  Overlooking the subtle differences in the actions of different types of topoisomerases (type I and type II).
  To avoid this, focus on the general function of topoisomerases as managing DNA topology.
 **Quick Tips**:
  1. Remember that topoisomerases work on the DNA's topology (shape and structure), not its sequence.
  2. Use mnemonics to remember the functions of key replication enzymes. For example, think of “Primase starts the primer”

D VINOD · Answer

Relieving torsional stress

D VINOD · Answer

Preventing supercoiling

D VINOD · Answer

Untangling DNA strands

D VINOD · Answer

The correct Option is "Synthesizing RNA primers"

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