DNA-templated DNA replication

Definition

Target type: biologicalprocess

A DNA replication process that uses parental DNA as a template for the DNA-dependent DNA polymerases that synthesize the new strands. [GOC:mah, ISBN:0198506732]

DNA replication is a fundamental process in all living organisms, where a double-stranded DNA molecule is copied to produce two identical DNA molecules. This process is essential for cell division and heredity. Here's a detailed description of the process:

**1. Initiation:**
- The process begins at specific sites on the DNA called origins of replication.
- The DNA molecule unwinds at the origin, forming a replication bubble.
- Two replication forks are formed at each end of the bubble, where replication proceeds bidirectionally.
- Specific proteins, including initiator proteins and helicase, unwind the DNA double helix.
- Single-stranded binding proteins (SSBs) stabilize the unwound strands, preventing them from re-annealing.

**2. Elongation:**
- DNA polymerase, the primary enzyme in DNA replication, synthesizes new DNA strands using the original strands as templates.
- DNA polymerase can only add nucleotides to the 3'-hydroxyl end of a pre-existing DNA strand.
- This leads to the synthesis of one continuous leading strand and one discontinuous lagging strand.
- The leading strand is synthesized continuously in the 5' to 3' direction.
- The lagging strand is synthesized in short fragments called Okazaki fragments, which are later joined together by DNA ligase.
- Primase, an RNA polymerase, synthesizes short RNA primers that provide a starting point for DNA polymerase.
- DNA polymerase removes the RNA primers and replaces them with DNA nucleotides.

**3. Termination:**
- As the replication forks progress, they eventually meet and terminate replication.
- The newly synthesized DNA molecules are separated, resulting in two identical DNA molecules.
- These molecules are then packaged into chromosomes and distributed to daughter cells during cell division.

**Key Enzymes and Proteins:**
- DNA polymerase: Synthesizes new DNA strands.
- Helicase: Unwinds the DNA double helix.
- Single-stranded binding proteins (SSBs): Stabilize the unwound strands.
- Primase: Synthesizes RNA primers.
- DNA ligase: Joins Okazaki fragments together.
- Topoisomerases: Relieve torsional stress in the DNA molecule.

**Accuracy and Fidelity:**
- DNA replication is remarkably accurate, with a very low error rate.
- This accuracy is ensured by several mechanisms, including:
- Proofreading activity of DNA polymerase.
- Mismatch repair systems that correct errors missed by DNA polymerase.

**Regulation:**
- DNA replication is tightly regulated to ensure that the genome is replicated only once per cell cycle.
- This regulation involves a complex network of proteins and signaling pathways.

**Importance of DNA Replication:**
- Essential for cell division and growth.
- Allows for the transmission of genetic information from one generation to the next.
- Provides the basis for genetic variation through mutations.
- Plays a role in various cellular processes, including repair and recombination.'
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Proteins (6)

Compounds (48)