Login-Verarbeitung ...

Trial ends in Request Full Access Tell Your Colleague About Jove

6.4: The DNA Replication Fork

JoVE Core
Molecular Biology

Ein Abonnement für JoVE ist erforderlich, um diesen Inhalt ansehen zu können. Melden Sie sich an oder starten Sie Ihre kostenlose Testversion.

The DNA Replication Fork

6.4: The DNA Replication Fork

An organism’s genome needs to be duplicated in an efficient and error-free manner for its growth and survival. The replication fork is a Y-shaped active region where two strands of DNA are separated and replicated continuously. The coupling of DNA unzipping and complementary strand synthesis is a characteristic feature of a replication fork.   Organisms with small circular DNA, such as E. coli, often have a single origin of replication; therefore, they have only two replication forks, one in each direction leading away from the location of the initial opening.  In organisms with large genomes, the replication of DNA is not done from a single point of origin but in many distinct, localized replication forks. 

The unhindered progression of the replication fork is necessary for complete DNA replication and genome stability; however, the replication fork is often stalled by internal or external factors that can slow or stop its progression, resulting in replication stress. Replication stress causes genomic instability, which is a hallmark of diseases like cancer. Genomic instability is characterized by genomic alterations and increased frequency of harmful mutations. The movement of the replication fork can stop due to several reasons. For example, the drug hydroxyurea depletes the pool of nucleotides available for incorporation into the daughter strand, stalling the replication fork. Other problems that may hinder the progression of the replication fork include DNA lesions, a collision between a replication fork and a transcription complex, and defects in the enzymes involved in DNA replication.

The cell has a variety of repair mechanisms to reinitiate the stalled replication fork.  S-phase checkpoints do not allow cells to begin mitosis until DNA repair is complete. Additionally, fork repriming can restart DNA synthesis by bypassing a DNA lesion or block. Despite these robust mechanisms, sometimes stalled forks cannot be reinitiated, which leads to the collapse of a fork, halting DNA replication.

Suggested Reading


DNA Replication Origin Of Replication DNA Helicase Replication Fork Single-stranded DNA Double-stranded Hairpin Loops Single-strand DNA Binding Proteins (SSBs) Complementary Daughter Strands Genome Duplication Efficient And Error-free Replication Circular DNA E. Coli

Get cutting-edge science videos from JoVE sent straight to your inbox every month.

Waiting X
Simple Hit Counter