Question

During DNA replication, which enzyme can be disposed of in an organism with a mutant DNA polymerase that does not require a free \(3^{\prime}-\mathrm{OH} ?\)

Short answer

Answer: Primase

Step-by-step solution

Understand the Function of DNA Polymerase

DNA polymerase is an important enzyme involved in DNA replication. Its main function is to add nucleotides to a growing DNA strand, synthesizing a new DNA molecule using one of the existing DNA strands as a template. DNA polymerase can only add nucleotides to an existing \(3^{\prime}-\mathrm{OH}\) group on the growing DNA strand.

Understand the Function of Primase

Primase is another enzyme involved in DNA replication. Its primary function is to synthesize short RNA primers, which provide a free \(3^{\prime}-\mathrm{OH}\) group for DNA polymerase to begin synthesizing the newly replicated strand.

Identify the Requirement for \(3^{\prime}-\mathrm{OH}\)

In normal DNA replication, the \(3^{\prime}-\mathrm{OH}\) group is required for DNA polymerase to attach nucleotides to the growing DNA strand. Primase synthesizes RNA primers, providing the \(3^{\prime}-\mathrm{OH}\) group for DNA polymerase to begin its function.

Identify the Mutant DNA Polymerase

In this exercise, the organism has a mutant DNA polymerase that does not require a free \(3^{\prime}-\mathrm{OH}\) group to initiate DNA replication. This means that the need for RNA primers synthesized by primase is no longer necessary.

Determine the Enzyme That Can Be Disposed Of

Since the mutant DNA polymerase does not require a free \(3^{\prime}-\mathrm{OH}\) group to initiate DNA replication, primase, which synthesizes RNA primers providing the \(3^{\prime}-\mathrm{OH}\) group for DNA polymerase, can be disposed of in the organism with a mutant DNA polymerase.

Key concepts

DNA Polymerase

DNA polymerase is a key enzyme in the DNA replication process. It performs the critical job of adding nucleotides to a growing DNA strand. This process involves following a DNA template to create a perfect copy of the genetic material. Think of DNA polymerase as a molecular builder. It reads the original DNA and matches complementary bases to extend the DNA strand.

One important requirement for DNA polymerase is a free 3'-OH group on the emerging DNA strand. This is the starting point necessary for the polymerase to attach new nucleotides. The enzyme moves along the DNA, adding nucleotides one by one to the 3' end.

• It reads the DNA template in a 3' to 5' direction.
• It synthesizes the new strand in a 5' to 3' direction.
• Works with RNA primers created by primase.

Primase

Primase is another crucial enzyme in the realm of DNA replication. Its main role is to create RNA primers, which are short segments of RNA. These primers provide the free 3'-OH group that DNA polymerase needs to start attaching nucleotides. You can think of primase as the starter tool for DNA replication. Without primers, DNA polymerase wouldn't find the necessary starting point on the strand.

Primase operates by synthesizing the initial RNA primer, which lays the foundation for DNA polymerase to function. Once this small RNA chunk is placed, DNA polymerase quickly takes over and starts extending the DNA strand.

• Primers are essential for initiating DNA synthesis.
• They are later removed and replaced by DNA sequences.
• Primase is an enzyme critical for starting the replication process.

RNA Primers

RNA primers are short snippets of RNA that play a pivotal role in DNA replication. They are the kickoff point that allows DNA polymerase to get to work. Generated by the enzyme primase, these primers offer the free 3'-OH group necessary for DNA polymerase action.

In the context of traditional DNA replication, RNA primers are indispensable. DNA polymerase requires these primers to begin nucleotide synthesis, as it cannot start without the 3'-OH group. However, in cases with mutant DNA polymerase that do not require this, the need for RNA primers could potentially be eliminated.

• RNA primers are temporary structures eventually replaced by DNA.
• Their presence is temporary but crucial for starting replication.
• RNA primers ensure that the growing DNA has a proper starting point.