​During replication, over-winding of DNA is caused by ____ and removed by ____:​

Correct option is C

During DNA replication, helicase unwinds the DNA double helix to create replication forks. This unwinding introduces positive supercoiling (over-winding) ahead of the replication fork. The enzyme gyrase, a type of topoisomerase, alleviates this supercoiling by introducing negative supercoils, ensuring smooth progression of the replication machinery. Without gyrase (or topoisomerase activity), the replication process would stall due to excessive tension.

Information Booster:

1. Helicase is responsible for unwinding the DNA strands, creating replication forks.
2. Positive supercoils form ahead of the replication fork due to the helicase activity.
3. Gyrase (a type of topoisomerase) relieves these supercoils, maintaining DNA topology.
4. Single-stranded binding proteins stabilize the unwound DNA strands.

      5.Proper coordination between helicase and topoisomerase is essential for efficient replication. Supercoiling occurs due to helicase activity during unwinding.

      6.Gyrase (topoisomerase) is essential to relieve over-winding and maintain DNA integrity.

      7. DNA replication requires the coordination of helicase, primase, topoisomerase, and single-stranded binding proteins.

Additional Knowledge:

• Helicase:
  This enzyme separates the two strands of DNA by breaking hydrogen bonds between complementary bases, enabling replication. It moves along the DNA in the 5′ to 3′ direction.
• Gyrase (Option c):
  A specialized type II topoisomerase found in prokaryotes, gyrase relieves positive supercoiling by cutting and resealing the DNA strands. It introduces negative supercoils to balance the tension caused by helicase activity.
• Primase (Option a, b):
  Primase synthesizes short RNA primers on the lagging strand to provide a starting point for DNA polymerase. It does not directly interact with supercoiling.
• Single-stranded binding proteins (Option b):
  These proteins bind to unwound DNA strands to prevent reannealing and protect the strands from nucleases, but they do not manage supercoiling.
• DNA Polymerase (Option d):
  This enzyme synthesizes new DNA strands but does not influence supercoiling directly.