Understanding Step 3 of DNA Replication: Elongation Phase and Polymerization Process

Step 3 of DNA replication

Step 3 of DNA replication is called the elongation or polymerization phase

Step 3 of DNA replication is called the elongation or polymerization phase. During this step, DNA polymerase synthesizes a new complementary strand of DNA using the existing template strand as a guide.

The process begins when the enzyme DNA polymerase binds to the RNA primer that was synthesized by the primase enzyme in step 2. The DNA polymerase moves along the template strand in the 3′ to 5′ direction, adding nucleotides to the growing daughter strand in the 5′ to 3′ direction.

The DNA polymerase contains an active site that is complementary to the nucleotide on the template strand. The enzyme recognizes the nucleotide at the replication fork and adds a complementary nucleotide to the growing daughter strand. The hydrogen bonds between the template strand and the newly incorporated nucleotide are formed, creating a stable bond.

As the DNA polymerase moves along the template strand, it continues to add nucleotides one by one to the growing daughter strand. It has proofreading capabilities, which allows it to detect and correct errors in the newly synthesized DNA. Any incorrect nucleotides are removed, and the correct nucleotides are inserted in their place.

The leading strand is synthesized in a continuous manner since the DNA polymerase can move continuously along the template strand in the 3′ to 5′ direction. In contrast, the lagging strand is synthesized discontinuously in short fragments called Okazaki fragments. The DNA polymerase synthesizes each Okazaki fragment in the opposite direction of the replication fork, creating small RNA primers that are eventually removed and replaced with DNA by the action of specialized enzymes.

The elongation phase continues until the entire DNA molecule has been replicated. At the end of this step, there are now two complete DNA molecules, each consisting of one original template strand and one newly synthesized daughter strand. These two DNA molecules are identical and are ready for the final step of DNA replication, which is called termination.

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