Question

DNA gyrase in E.coli are required in replication to

• A. make isomeric copies of DNA replicating enzymes
• B. synthesise short chains of nucleotides to prime DNA chain elongation
• C. relieve the supercoiling that arises from DNA unwinding mediated by helicase
• D. introduce chirality in DNA molecules

Answer 1

The correct option is C relieve the supercoiling that arises from DNA unwinding mediated by helicase

During replication, gyrases help to relieve and release tension created by the unwinding process of DNA helicase enzyme. DNA gyrase has the ability to remove positive supercoiling(DNA twisted in a right-handed fashion and it starts to knot and distort).
Although, such classes of enzymes have different types but their basic function remains the same i.e., to relieve the tension generated by supercoiling of DNA. This supercoiling may be positive or even negative(DNA twisted in a left-handed fashion and it starts to knot and distort) in many cases.

These enzymes neither make isomeric copies of DNA replicating enzymes nor introduce chirality(non-superimposable mirror images) in DNA molecules.

Short chains of nucleotides are synthesised by primase to prime DNA elongation. DNA elongation is brought about by DNA polymerase.