Final answer:
The correct option is True. The statement is true; proteins do generate double-stranded DNA circles from the tail produced by rolling circle replication. This process involves nicking one strand of DNA, synthesizing a new strand, displacing the old strand, and then using the newly formed ssDNA to create a complementary strand resulting in dsDNA.
Step-by-step explanation:
The statement that a protein generates double-stranded circles from the tail produced by rolling circle replication is True. Rolling circle replication is a process utilized by certain plasmids, bacteriophages, and viruses for DNA synthesis. This method starts with one strand of a double-stranded circular DNA being nicked, which allows DNA polymerase III to bind and synthesize a new strand using the intact original strand as a template.
The original nicked strand is displaced during this synthesis. After replication, the displaced single-stranded DNA (ssDNA) can recircularize and serve as a template for the synthesis of a complementary strand, creating a double-stranded DNA (dsDNA) circle.
During rolling circle replication, enzymes play critical roles. Topoisomerase II, DNA gyrase in bacteria, relaxes the supercoiled DNA. Helicase separates the strands, and single-strand binding proteins stabilize the single-stranded regions.
Assembly of a new DNA strand is initiated by primase, which synthesizes a primer at the single-stranded origin (sso) site. DNA polymerase III then elongates this primer, leading to the formation of double-stranded DNA. The process involves the generation of single-stranded DNA from which double-stranded circles can be produced, confirming the correctness of the initial statement.