How does dna get copied accurately

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Recovering a Stalled Replication Fork. Aging and Cell Division. Germ Cells and Epigenetics. Citation: Noguchi, E. Nature Education 3 9 The replication fork is more than just a means for DNA duplication.

It is connected to a checkpoint system that keeps the genome intact and prevents cancer. Aa Aa Aa. Figure 1: Obstacles on DNA that generate stalled replication forks. Figure Detail.

Figure 2: Checkpoint responses. Figure 3: Fork protection. Most of the mistakes during DNA replication are promptly corrected by DNA polymerase by proofreading the base that has just been added Figure 1. In proofreading , the DNA pol reads the newly added base before adding the next one, so a correction can be made.

The polymerase checks whether the newly added base has paired correctly with the base in the template strand. If it is the right base, the next nucleotide is added.

If an incorrect base has been added, the enzyme makes a cut at the phosphodiester bond and releases the wrong nucleotide. Once the incorrect nucleotide has been removed, a new one will be added again. Figure 1. Proofreading by DNA polymerase corrects errors during replication. Some errors are not corrected during replication, but are instead corrected after replication is completed; this type of repair is known as mismatch repair Figure 2.

The enzymes recognize the incorrectly added nucleotide and excise it; this is then replaced by the correct base. If this remains uncorrected, it may lead to more permanent damage. From left to right, the complementary nucleotides in the bottom row are: thymine red , guanine blue , adenine green , and cytosine orange. Figure 5: A new DNA strand is synthesized.

This strand contains nucleotides that are complementary to those in the template sequence. How long does replication take? More on replication. How does DNA polymerase work? What does the molecular structure of a nucleotide look like? What does the lagging strand look like?

Watch this video for a summary of DNA replication in eukaryotes. Key Questions What if an error happens during replication? How is DNA stored in the cell before and after replication? What do the leading and lagging strands look like when they are being replicated? Key Concepts DNA polymerase primer transcription. Topic rooms within Genetics Close. No topic rooms are there. Browse Visually. Other Topic Rooms Genetics.

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