Question

Where is the DnaB helicase first loaded onto the DNA? a. at the replication terminator site

b. at the replication origin
c. at random locations through the circular chromosome
d. at the operator
e. at the promoter

Answer 1

DnaB helicase is first loaded at the replication origin, where it unwinds the DNA and initiates the replication process by forming Y-shaped replication forks. This occurs at specific sequences and allows DNA replication to proceed bidirectionally.

Step-by-step explanation:

DnaB helicase is first loaded onto the DNA at the replication origin. The origin of replication is a specific nucleotide sequence recognized by certain proteins that facilitate the binding of helicase. This enzyme then unwinds the DNA, breaking hydrogen bonds between base pairs and initiating the replication process by forming Y-shaped replication forks, extending bidirectionally.

During DNA replication, the helicase is crucial for separating the two strands of the DNA double helix so replication machinery can synthesize new DNA strands. It effectively moves ahead of replication, continuously unwinding the DNA at the replication forks so that the DNA polymerase enzyme can add new nucleotides.