Answer :
The PET strain with impaired supercoiling likely has a mutated DNA gyrase, which is crucial for relaxing supercoiled chromosomes in bacteria. When the joining of Okazaki fragments is impaired, DNA ligase is probably the mutated enzyme involved in connecting these DNA segments during replication.Therefore, the correct answer is option a. DNA gyrase.
The strain identified with impaired supercoiling of the bacterial chromosome likely carries a mutation in DNA gyrase (topoisomerase II), which is a bacterial topoisomerase responsible for relaxing the supercoiled chromosome to make DNA more accessible for the initiation of replication. This process is critical in prokaryotes like bacteria, as it allows for the control of DNA under- or over-winding during processes such as replication. DNA gyrase is also a target for a variety of antibiotics, emphasizing its importance in bacterial cell function.
In the case where the joining together of Okazaki fragments is impaired, the most likely mutated enzyme at the replication fork is DNA ligase. DNA ligase is responsible for joining the Okazaki fragments to create a continuous DNA strand during lagging strand synthesis. Its malfunction would directly affect the proper joining of these fragments.
