DNA strand elongation

Definition

Target type: biologicalprocess

The DNA metabolic process in which an existing DNA strand is extended by activities including the addition of nucleotides to the 3' end of the strand. [GOC:isa_complete, GOC:mah]

DNA strand elongation is a fundamental process in DNA replication, where a new DNA strand is synthesized using an existing DNA strand as a template. The process involves several key steps:

1. **Initiation:** The process starts with the unwinding of the DNA double helix, breaking the hydrogen bonds between the base pairs. This unwinding is catalyzed by enzymes called helicases. Single-stranded binding proteins (SSBs) then bind to the single-stranded DNA to prevent it from re-annealing.

2. **Primer Synthesis:** A short RNA primer, typically around 10 nucleotides long, is synthesized by an enzyme called primase. The primer provides a free 3' hydroxyl group, which is essential for the initiation of DNA synthesis.

3. **Elongation:** DNA polymerase, the primary enzyme involved in DNA replication, binds to the primer and starts adding nucleotides to the 3' end of the primer, following the base pairing rules (adenine with thymine, guanine with cytosine). This process is known as 5' to 3' synthesis. The DNA polymerase uses the template strand as a guide, ensuring that the newly synthesized strand is complementary to the original DNA strand.

4. **Leading and Lagging Strand Synthesis:** Due to the antiparallel nature of DNA, the two strands are synthesized differently. One strand, called the leading strand, is synthesized continuously in the 5' to 3' direction. The other strand, called the lagging strand, is synthesized discontinuously in short fragments called Okazaki fragments. Each Okazaki fragment requires a new primer, and the fragments are later joined together by DNA ligase.

5. **Proofreading:** DNA polymerase has a built-in proofreading mechanism. It can detect and remove incorrectly incorporated nucleotides, ensuring high fidelity of DNA replication.

6. **Termination:** The process of elongation ends when the polymerase reaches a specific termination sequence on the DNA template.

In summary, DNA strand elongation involves the unwinding of the DNA double helix, synthesis of an RNA primer, and the sequential addition of nucleotides to the 3' end of the primer by DNA polymerase, using the template strand as a guide. This process is essential for accurate replication of genetic information, ensuring the transmission of genetic traits from one generation to the next.'
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Proteins (1)

Compounds (28)