# [DNA Replication](/blog/guides/dna-replication) Direction: Why It Goes from 5' to 3'


## Key Takeaways

- DNA polymerases catalyze nucleotide addition exclusively at the 3' hydroxyl group of the growing polynucleotide chain, dictating a mandatory 5' to 3' synthesis direction. This is driven by the nucleophilic attack of the 3' OH on the α-phosphate of an incoming deoxyribonucleoside triphosphate (dNTP), releasing pyrophosphate.
- The antiparallel orientation of DNA strands necessitates continuous synthesis on the leading strand (template read 3' to 5') and discontinuous synthesis of Okazaki fragments on the lagging strand (template read 5' to 3').
- DNA polymerases require a pre-existing 3' hydroxyl group to initiate synthesis; this is provided by RNA primers synthesized by primase, a specialized RNA polymerase.
- The 5' to 3' directionality leads to the end-replication problem in linear chromosomes, where the lagging strand's 5' end cannot be fully replicated after primer removal, resulting in progressive telomere shortening.
- Telomerase, a ribonucleoprotein reverse transcriptase, counteracts telomere shortening by extending the 3' overhang of telomeres using its intrinsic RNA template, thereby providing sufficient template for lagging strand completion.

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## Introduction to DNA Replication Directionality

DNA replication is the process by which a cell duplicates its entire genome before division. Every time a human cell divides, it must accurately copy approximately 3.2 billion base pairs. The remarkable fidelity of this process—roughly one error per 10⁹ to 10¹⁰ nucleotides incorporated—depends on a fundamental biochemical constraint: DNA polymerases can only synthesize new DNA in the 5' to 3' direction. This directionality is not arbitrary; it is dictated by the chemistry of nucleotide addition, the structure of the enzyme's active site, and the energetic requirements of phosphodiester bond formation.

### The Structure of DNA and Nucleotide Polarity

To understand directionality, you must first understand the chemical polarity of the DNA molecule. Each nucleotide consists of three components: a nitrogenous base (adenine, guanine, cytosine, or thymine), a five-carbon deoxyribose sugar, and one or more phosphate groups. The sugar ring contains five carbon atoms, numbered 1' through 5' (the prime notation distinguishes these carbons from the nitrogenous base atoms). The 1' carbon attaches to the base, the 3' carbon bears a hydroxyl (–OH) group, and the 5' carbon carries a phosphate group.

When nucleotides are linked together into a polynucleotide chain, the phosphate group attached to the 5' carbon of one nucleotide forms a phosphodiester bond with the hydroxyl group on the 3' carbon of the adjacent nucleotide. This creates a sugar-phosphate backbone with an inherent polarity: one end of the chain has a free 5' phosphate group (the 5' end), and the other end has a free 3' hydroxyl group (the 3' end). By convention, DNA sequences are written from 5' to 3', left to right.

The two strands of the [DNA double helix](/blog/guides/dna-double-helix) run in opposite directions—they are antiparallel. One strand runs 5' to 3' in a given direction, while the complementary strand runs 3' to 5' in that same direction. This antiparallel arrangement is essential for the base-pairing geometry of the double helix and has profound consequences for how replication proceeds.

### The Central Dogma and Replication

DNA replication is one arm of [the central dogma of molecular biology](/blog/news/the-central-dogma-of-molecular-biology) (DNA → DNA → RNA → protein). The process is semiconservative: each daughter molecule contains one parental strand and one newly synthesized strand, as demonstrated by the Meselson-Stahl experiment. Replication begins at specific sequences called origins of replication, where the double helix is unwound to form a [Replication Fork Definition](/knowledge/molecular-biology/replication-fork-definition). The replication fork is the Y-shaped region where active synthesis occurs, and it is here that the directionality of DNA polymerases becomes critically important.

## The Chemical Basis: Why Polymerases Add Nucleotides Only to the 3' End

### The Role of the 3' OH Group

The fundamental reaction catalyzed by all DNA polymerases is a nucleophilic attack. The 3' hydroxyl group (–OH) at the growing end of the DNA chain acts as a nucleophile, attacking the α-phosphate of an incoming deoxyribonucleoside triphosphate (dNTP). This reaction forms a new phosphodiester bond between the 3' oxygen of the growing chain and the α-phosphate of the incoming nucleotide.

The incoming dNTP is a high-energy molecule: it carries three phosphate groups (α, β, and γ) attached to the 5' carbon of the deoxyribose sugar. During polymerization, the bond between the α and β phosphates is broken, releasing pyrophosphate (PPi, two phosphate groups). The subsequent hydrolysis of pyrophosphate into two inorganic phosphate molecules by the enzyme pyrophosphatase drives the reaction forward, making the overall process thermodynamically favorable.

The key chemical constraint is that the 3' hydroxyl group is the only nucleophile available in the growing chain. The 5' end of the chain terminates in a phosphate group, which cannot act as a nucleophile in this reaction. A phosphate group has no hydrogen atom to donate in the formation of a new bond; it is already fully substituted with oxygen atoms. Therefore, extension can only occur at the 3' end, where a free hydroxyl group is available.

### Energy Requirements and Pyrophosphate Release

The polymerization reaction is energetically coupled to pyrophosphate hydrolysis. The free energy change (ΔG°) for phosphodiester bond formation is approximately –5.3 kcal/mol when pyrophosphate hydrolysis is included. Without this coupling, the reaction would be thermodynamically unfavorable. The release of pyrophosphate and its subsequent cleavage into two phosphates ensures that the reaction proceeds essentially irreversibly in the forward direction.

This energetic requirement reinforces the 5' to 3' directionality. If a polymerase were to attempt synthesis in the 3' to 5' direction, it would need to activate the 5' phosphate group of the growing chain—a chemically distinct and much more difficult reaction. No known DNA polymerase has evolved to catalyze this reaction, and the energetic barrier is prohibitive.

## DNA Polymerase Structure and Active Site Geometry

### The Palm, Fingers, and Thumb Domains

DNA polymerases share a conserved three-dimensional architecture that resembles a right hand. The three domains—palm, fingers, and thumb—work together to ensure that only 3' extension occurs.

The **palm domain** contains the catalytic residues that coordinate the two metal ions (typically Mg²⁺) required for catalysis. These metal ions are positioned to stabilize the negative charges that develop during the nucleophilic attack and to orient the incoming dNTP correctly. The palm domain also contains the binding site for the 3' end of the primer strand, positioning the 3' hydroxyl group precisely for attack on the α-phosphate of the incoming nucleotide.

The **fingers domain** undergoes a conformational change when the correct incoming dNTP binds. This domain interacts with the template strand and the incoming nucleotide, checking that the base pairing is correct. The fingers domain closes around the incoming nucleotide, bringing it into the active site where the 3' OH can attack.

The **thumb domain** binds the duplex DNA product, helping to hold the primer-template junction in place. The thumb also plays a role in processivity—the ability of the polymerase to add many nucleotides without dissociating from the template.

The geometry of the active site is critical: the 3' hydroxyl of the primer is positioned within a few angstroms of the α-phosphate of the incoming dNTP. The 5' end of the growing chain is far from the catalytic center and cannot be brought into the active site. This structural arrangement makes 5' to 3' synthesis the only chemically and geometrically possible direction.

### Proofreading and the 3' to 5' Exonuclease Activity

Many DNA polymerases possess a separate 3' to 5' exonuclease activity that removes mismatched nucleotides. This proofreading function is located in a distinct domain, often near the palm. When a misincorporated nucleotide is detected, the polymerase pauses, and the primer strand is threaded into the exonuclease active site, where the mismatched nucleotide is removed.

The proofreading activity is itself directional: it removes nucleotides from the 3' end of the growing chain, one at a time. This is the opposite direction of synthesis. The polymerase alternates between polymerization (5' to 3') and proofreading (3' to 5'), depending on whether the terminal base pair is correct. This bidirectional capability within a single enzyme is possible because the two active sites are physically separate and the primer strand can be shuttled between them.

The proofreading exonuclease increases replication fidelity by approximately 100-fold. Without it, the error rate would be roughly 10⁻⁵ to 10⁻⁶; with proofreading, it drops to about 10⁻⁷ to 10⁻⁸. Post-replication [mismatch repair](/knowledge/molecular-biology/mismatch-repair) systems further improve fidelity to the final 10⁻⁹ to 10⁻¹⁰.

## The Antiparallel Nature of DNA and the Leading and Lagging Strands

### Continuous Synthesis on the Leading Strand

The antiparallel arrangement of the double helix creates an immediate problem for the replication machinery. At the [Replication Fork Helicase](/knowledge/molecular-biology/replication-fork-helicase) unwinds the double helix, the two template strands are exposed in opposite orientations. One template strand runs 3' to 5' in the direction of fork movement, and the other runs 5' to 3'.

Because DNA polymerase can only synthesize in the 5' to 3' direction, the strand whose template runs 3' to 5' (relative to fork movement) can be synthesized continuously. This is the **leading strand**. As the fork unwinds, the polymerase moves along the template in the same direction as the fork, adding nucleotides continuously.

The leading strand requires only one priming event at the origin of replication. Once the primer is in place, the polymerase can processively add thousands of nucleotides without stopping.

### [Okazaki Fragments](/knowledge/molecular-biology/okazaki-fragment) and the Lagging Strand

The other template strand runs 5' to 3' in the direction of fork movement. To synthesize a new strand in the 5' to 3' direction, the polymerase must move in the opposite direction to the fork. This creates a problem: the polymerase cannot keep up with the unwinding fork if it moves backward.

The solution is discontinuous synthesis. The lagging strand is synthesized in short segments called **Okazaki fragments**, typically 100–200 nucleotides long in eukaryotes and 1,000–2,000 nucleotides in bacteria. Each fragment is initiated by a new RNA primer, and the polymerase extends the primer until it reaches the previous fragment. The fragments are then joined together by DNA ligase.

The lagging strand template is thought to loop out, allowing the polymerase to synthesize a fragment while remaining physically associated with the replication machinery. This looping mechanism, mediated by the replication clamp and clamp loader, ensures that both strands are synthesized coordinately at the fork.

The existence of Okazaki fragments is a direct consequence of the 5' to 3' directionality of DNA polymerases. If polymerases could synthesize in the 3' to 5' direction, both strands could be synthesized continuously, and the elaborate machinery for lagging strand synthesis would be unnecessary.

## The Role of RNA Primers and Primase

### Primase and the Initiation of Synthesis

DNA polymerases cannot initiate synthesis de novo. They require a free 3' hydroxyl group to which they can add the first nucleotide. This is because the active site is designed to accept a primer-template junction, not a bare template. The enzyme must have a duplex region to bind, and the primer must provide the 3' OH for the first nucleophilic attack.

To solve this problem, cells use an enzyme called **primase**, which synthesizes short RNA primers (approximately 10–12 nucleotides in eukaryotes, 10–60 in bacteria) complementary to the template. Primase is a specialized RNA polymerase that can initiate synthesis de novo, without a primer. It does so by using the template to position the first two ribonucleotides and catalyzing the formation of the first phosphodiester bond.

The RNA primer provides the free 3' OH group that DNA polymerase requires. The polymerase then extends the primer with deoxyribonucleotides, adding to the 3' end of the RNA primer. On the leading strand, only one primer is needed at the origin. On the lagging strand, a new primer is required for each [Okazaki fragment](/knowledge/molecular-biology/okazaki-fragment).

### Removal of RNA Primers and Gap Filling

After the Okazaki fragments are synthesized, the RNA primers must be removed and replaced with DNA. In bacteria, this is accomplished by DNA polymerase I, which has both 5' to 3' exonuclease activity (to remove the RNA primer ahead of it) and 5' to 3' polymerase activity (to fill the gap with DNA). The enzyme simultaneously removes the RNA primer and synthesizes DNA to replace it, moving in the 5' to 3' direction.

In eukaryotes, the removal of RNA primers is more complex. The enzyme RNase H2 (ribonuclease H2) removes most of the RNA primer, leaving a single ribonucleotide at the junction. The flap endonuclease FEN1 then removes this remaining ribonucleotide. The gap is filled by DNA polymerase δ or ε, and the nick is sealed by DNA ligase I.

The requirement for RNA primers is another consequence of the 5' to 3' directionality. If DNA polymerases could initiate synthesis de novo, primers would be unnecessary. The fact that every DNA polymerase requires a pre-existing 3' OH—whether from an RNA primer, a nick, or a previous Okazaki fragment—underscores the fundamental nature of this constraint.

## Experimental Evidence for 5' to 3' Synthesis

### Pulse-Chase Experiments with Radioactive Nucleotides

The direction of DNA synthesis was established through elegant experiments using radioactive labeling. In a pulse-chase experiment, cells are briefly exposed to a radioactive nucleotide (the pulse), followed by a longer exposure to non-radioactive nucleotides (the chase). By analyzing the location of the radioactive label at different times, researchers can determine the direction of synthesis.

In a classic experiment, cells were pulsed with ³H-thymidine (tritiated thymidine) for a very short time, then chased with unlabeled thymidine. The DNA was then extracted and digested with exonucleases that specifically remove nucleotides from either the 5' or 3' end. By measuring the radioactivity released at each time point, researchers could determine whether the newly synthesized DNA was added to the 3' end (label would be released by 3' exonuclease digestion) or the 5' end (label released by 5' exonuclease digestion).

The results consistently showed that the radioactive label was incorporated at the 3' end of the growing chain. This demonstrated that new nucleotides are added to the 3' end, meaning synthesis proceeds in the 5' to 3' direction.

### Kornberg's In Vitro Replication Assays

Arthur Kornberg's pioneering work in the 1950s established the enzymatic basis of DNA replication. He purified DNA polymerase I from *Escherichia coli* and demonstrated that it could synthesize DNA in vitro using a template, a primer, and the four dNTPs. Kornberg's assay included:

1. A DNA template (either single-stranded or duplex DNA)
2. A primer with a free 3' OH
3. All four dNTPs (dATP, dGTP, dCTP, dTTP), one of which was radioactively labeled
4. Mg²⁺ ions (typically 5–10 mM)
5. Tris buffer (pH 7.4–8.0)
6. The polymerase enzyme

The reaction was incubated at 37°C, and incorporation of radioactivity into acid-precipitable DNA was measured over time. Kornberg showed that DNA synthesis required all four dNTPs, a template, and a primer. He also demonstrated that the reaction was template-directed: the base composition of the product mirrored that of the template.

Kornberg's in vitro system was instrumental in determining the direction of synthesis. By using primers with specifically labeled ends and analyzing the products, his laboratory confirmed that DNA polymerase adds nucleotides to the 3' end of the primer, extending it in the 5' to 3' direction. Kornberg was awarded the Nobel Prize in Physiology or Medicine in 1959 for this work.

## Common Misconceptions: Why DNA Replication Does Not Go from 3' to 5'

### Template Reading vs. New Strand Synthesis

A frequent source of confusion is the distinction between the direction of template reading and the direction of new strand synthesis. The template strand is read in the 3' to 5' direction, while the new strand is synthesized in the 5' to 3' direction. These two directions are complementary and antiparallel.

When we say "the template is read 3' to 5'," we mean that the polymerase moves along the template from its 3' end toward its 5' end. As it does so, it adds nucleotides to the 3' end of the growing new strand. The new strand is therefore synthesized in the 5' to 3' direction.

Consider a template with the sequence 5'-ATGC-3'. The polymerase reads this template from the 3' end (the C) toward the 5' end (the A). The new strand will be synthesized as 3'-TACG-5', which is written as 5'-GCAT-3' in the conventional 5' to 3' direction. The new strand is antiparallel to the template.

### The Meaning of 'Antiparallel'

The term "antiparallel" refers to the opposite orientation of the two strands in the [DNA double helix](/blog/guides/dna-double-helix). One strand runs 5' to 3' in a given direction, and the other runs 3' to 5'. This is not a mere convention; it is a structural requirement of the double helix. The base-pairing geometry—specifically, the angles of the glycosidic bonds and the positions of the sugar-phosphate backbones—requires that the two strands run in opposite directions.

When DNA is replicated, the antiparallel nature of the double helix means that the two new strands must be synthesized in opposite directions relative to the fork. This is why one strand (the leading strand) is synthesized continuously in the same direction as fork movement, while the other (the lagging strand) is synthesized discontinuously in the opposite direction.

## Consequences of Directionality: Replication Errors and [Telomere Shortening](/knowledge/molecular-biology/telomere-shortening)

### The End-Replication Problem

The 5' to 3' directionality of DNA polymerases creates a specific problem at the ends of linear chromosomes. When the replication fork reaches the end of a chromosome, the lagging strand cannot be fully replicated. The final Okazaki fragment requires an RNA primer, but there is no template beyond the chromosome end to position the primer. When the RNA primer is removed, a gap remains at the 5' end of the newly synthesized lagging strand.

This is the **end-replication problem**: each round of replication shortens the chromosome by the length of the terminal RNA primer (approximately 50–200 nucleotides in humans). Without a mechanism to counteract this shortening, chromosomes would progressively erode with each cell division, leading to loss of genetic information and eventual cell death.

### Telomerase and Its Role in Extending the 3' End

The solution to the end-replication problem is the enzyme **telomerase**. Telomerase is a ribonucleoprotein that contains an RNA component (TERC, telomerase RNA component) and a catalytic protein subunit (TERT, telomerase reverse transcriptase). The RNA component contains a short template sequence that is complementary to the telomeric repeat sequence (TTAGGG in vertebrates).

Telomerase extends the 3' end of the telomere by using its RNA template to add telomeric repeats. This is a reverse transcription reaction: telomerase synthesizes DNA using an RNA template. The enzyme binds to the 3' overhang of the telomere, adds nucleotides complementary to its RNA template, then translocates and repeats the process.

By extending the 3' end of the telomeric DNA, telomerase provides additional template for lagging strand synthesis. The extended 3' overhang can then be filled in by the normal lagging strand machinery, including primase, DNA polymerase, and ligase. This prevents the progressive shortening that would otherwise occur.

Telomerase is active in germ cells, stem cells, and most cancer cells, but is inactive in most somatic cells. The progressive shortening of telomeres in somatic cells is thought to contribute to cellular aging and the limited replicative lifespan of cells in culture (the Hayflick limit).

## Practical Summary and Study Tips


### Common Exam Questions and How to Answer Them

**Question: Why can't DNA polymerase synthesize in the 3' to 5' direction?**

Answer: The 3' to 5' direction would require the 5' phosphate of the growing chain to act as an electrophile, attacking the incoming nucleotide. This is chemically unfavorable because the 5' phosphate is already fully substituted and cannot form a new bond without first being activated. The 3' hydroxyl is the only nucleophile available, and the polymerase active site is geometrically arranged to position the 3' OH for attack on the α-phosphate of the incoming dNTP.

**Question: What is the difference between the leading and lagging strands?**

Answer: The leading strand is synthesized continuously in the same direction as fork movement, requiring only one primer. The lagging strand is synthesized discontinuously in the opposite direction, requiring multiple primers and producing Okazaki fragments that are later joined by DNA ligase. This asymmetry arises because the two template strands are antiparallel, and the polymerase can only synthesize in the 5' to 3' direction.

**Question: Why is the template read 3' to 5'?**

Answer: The template is read 3' to 5' because the polymerase moves along the template in that direction while synthesizing the new strand in the 5' to 3' direction. The two strands are antiparallel, so the direction of synthesis on the new strand determines the direction of movement on the template.

## Common Pitfalls

**Pitfall 1: Confusing the direction of synthesis with the direction of template reading.** Remember: synthesis is always 5' to 3'; template reading is always 3' to 5'. These are two sides of the same coin.

**Pitfall 2: Thinking that the leading strand is synthesized in the 3' to 5' direction.** The leading strand is synthesized in the 5' to 3' direction, just like the lagging strand. The difference is that the leading strand is synthesized continuously, while the lagging strand is synthesized discontinuously.

**Pitfall 3: Believing that DNA polymerase can initiate synthesis de novo.** DNA polymerase requires a pre-existing 3' OH group. This is provided by an RNA primer, a nick, or the 3' end of a previous Okazaki fragment.

**Pitfall 4: Forgetting that the proofreading exonuclease works in the 3' to 5' direction.** The proofreading activity removes nucleotides from the 3' end of the growing chain. This is the opposite direction of synthesis and is a separate activity from polymerization.

**Pitfall 5: Assuming that the end-replication problem affects both strands equally.** The end-replication problem specifically affects the lagging strand, because the terminal RNA primer cannot be replaced with DNA. The leading strand can be replicated to the very end of the chromosome.

## Frequently Asked Questions

### Does DNA replication go from 3 to 5?

No. DNA replication always proceeds in the 5' to 3' direction. The template strand is read in the 3' to 5' direction, but the new strand is always synthesized in the 5' to 3' direction. This is a fundamental property of all DNA polymerases.

### Why does DNA replication go from 5 to 3?

DNA replication goes from 5' to 3' because the 3' hydroxyl group of the growing chain is the only nucleophile available to attack the α-phosphate of the incoming nucleotide. The 5' end of the chain terminates in a phosphate group that cannot participate in this reaction. Additionally, the active site of DNA polymerase is geometrically arranged to position the 3' OH for catalysis, and the energy released by pyrophosphate hydrolysis drives the reaction forward.

### What does it mean that DNA synthesis is 5' to 3'?

It means that new nucleotides are added to the 3' end of the growing DNA chain. The 3' hydroxyl group of the terminal nucleotide attacks the α-phosphate of the incoming dNTP, forming a new phosphodiester bond. The chain therefore grows by extension at its 3' end, and the 5' end remains unchanged throughout the process.

### Why is the template read 3' to 5'?

The template is read 3' to 5' because the polymerase moves along the template in that direction while synthesizing the new strand in the 5' to 3' direction. The two strands are antiparallel, so the direction of synthesis on the new strand determines the direction of movement on the template.

### Can DNA polymerase synthesize in the 3' to 5' direction?

No. No known DNA polymerase can synthesize in the 3' to 5' direction. The chemistry of the reaction, the structure of the active site, and the energetic requirements all preclude this direction. Some polymerases have a 3' to 5' exonuclease activity for proofreading, but this removes nucleotides rather than adding them.

### What is the role of the 3' OH group in DNA replication?

The 3' OH group is the nucleophile that attacks the α-phosphate of the incoming dNTP to form a new phosphodiester bond. It is essential for polymerization; without a free 3' OH, DNA polymerase cannot add nucleotides. This is why RNA primers are required to initiate synthesis.

### Why are Okazaki fragments formed on the lagging strand?

Okazaki fragments are formed on the lagging strand because the template strand runs 5' to 3' in the direction of fork movement. Since DNA polymerase can only synthesize in the 5' to 3' direction, it must synthesize the lagging strand in the opposite direction to the fork. This requires discontinuous synthesis in short fragments, each initiated by a new RNA primer.

## Key Takeaways

- DNA polymerases synthesize new DNA exclusively in the 5' to 3' direction, adding nucleotides to the 3' hydroxyl group of the growing chain.
- The chemical basis for this directionality is the nucleophilic attack of the 3' OH on the α-phosphate of the incoming dNTP, coupled to pyrophosphate hydrolysis.
- The template strand is read in the 3' to 5' direction, and the new strand is synthesized antiparallel to it in the 5' to 3' direction.
- The antiparallel nature of the double helix forces continuous synthesis on the leading strand and discontinuous synthesis (Okazaki fragments) on the lagging strand.
- DNA polymerases cannot initiate synthesis de novo; they require a free 3' OH provided by an RNA primer synthesized by primase.
- The 5' to 3' directionality leads to the end-replication problem at chromosome termini, which is solved by the enzyme telomerase.
- Understanding the chemistry of phosphodiester bond formation is the key to understanding all downstream consequences of replication directionality.

## Further Reading

- Masuda-Sasa T et al. *Processing of G4 DNA by Dna2 helicase/nuclease and replication protein A (RPA) provides insights into the mechanism of Dna2/RPA substrate recognition*. The Journal of biological chemistry. 2008. [PubMed 18593712](https://doi.org/10.1074/jbc.M802244200)
- Deshmukh AL et al. *Dynamics of replication proteins during lagging strand synthesis: A crossroads for genomic instability and cancer*. DNA repair. 2016. [PubMed 27161865](https://doi.org/10.1016/j.dnarep.2016.04.010)
- Akagi JI et al. *A formamidopyrimidine derivative from the deoxyguanosine adduct produced by food contaminant acrylamide induces DNA replication block and mutagenesis*. The Journal of biological chemistry. 2023. [PubMed 37394003](https://doi.org/10.1016/j.jbc.2023.105002)

## Related Topics

- [Helicase Move 3 to 5](/knowledge/molecular-biology/helicase-move-3-to-5)
- [DNA Replication Occur Before Mitosis](/knowledge/molecular-biology/dna-replication-occur-before-mitosis)
- [DNA Polymerase 1 2 3](/knowledge/molecular-biology/dna-polymerase-1-2-3)
- [DNA Replication Part of Central Dogma](/knowledge/molecular-biology/dna-replication-part-of-central-dogma)
- [DNA Replication Notes Grade 12](/knowledge/molecular-biology/dna-replication-notes-grade-12)

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