Question

List the substances required for replication of DNA catalyzed by DNA polymerase.

Short answer

DNA Polymerase, single-stranded DNA template, dNTPs (dATP, dTTP, dGTP, dCTP), primer, helicase, single-strand binding proteins, and primase.

Step-by-step solution

Identify the Enzyme

The enzyme catalyzing the replication of DNA is DNA polymerase.

Determine the Template

A single-stranded DNA template is required for the DNA polymerase to add nucleotides in a complementary manner.

Identify the Nucleotides

Deoxyribonucleoside triphosphates (dNTPs) are the building blocks for DNA synthesis. The four types are dATP, dTTP, dGTP, and dCTP.

Primer Requirements

A short RNA or DNA primer with a free 3'-hydroxyl group is necessary for DNA polymerase to begin synthesis.

Accessory Proteins

Additional proteins such as helicase (to unwind the DNA), single-strand binding proteins (to prevent reannealing), and primase (to synthesize the RNA primer) are also needed.

Key concepts

DNA polymerase

DNA polymerase is a crucial enzyme in DNA replication. It catalyzes the addition of nucleotides to a growing DNA strand. DNA polymerase reads the template strand and incorporates complementary nucleotides to form a new strand. It ensures high fidelity in DNA replication by proofreading each nucleotide base pair added, reducing the chance of errors.

Single-stranded DNA template

During DNA replication, a single-stranded DNA template is essential. This template provides the pattern for building a complementary DNA strand. The DNA double helix is unwound by helicase, resulting in two single strands. Each single-stranded DNA serves as a template for the formation of a new complementary strand by DNA polymerase.

Deoxyribonucleoside triphosphates (dNTPs)

Deoxyribonucleoside triphosphates (dNTPs) are the building blocks of DNA. These molecules are dATP, dTTP, dGTP, and dCTP. Each dNTP consists of a nitrogenous base, a deoxyribose sugar, and three phosphate groups. DNA polymerase uses these dNTPs to synthesize the new DNA strand by adding them to the growing chain, releasing two phosphates.

RNA primer

An RNA primer is a short segment of RNA that provides a starting point for DNA synthesis. Primase synthesizes this RNA primer, which has a free 3'-hydroxyl group. DNA polymerase cannot begin synthesis on a bare template; it requires this RNA primer to which it can add nucleotides. The primer is later removed and replaced with DNA.

Helicase

Helicase is an enzyme that unwinds the DNA double helix. It separates the two strands of DNA, creating single-stranded templates necessary for replication. Helicase breaks the hydrogen bonds between the base pairs, allowing the replication fork to move and enabling the DNA polymerase to access the single-stranded template for synthesis.

Single-strand binding proteins

Single-strand binding proteins (SSBs) are crucial in DNA replication. They bind to the single-stranded DNA after helicase unwinds it, preventing the strands from re-annealing or forming secondary structures. SSBs stabilize the single-stranded DNA, ensuring it remains open and accessible for the DNA polymerase to synthesize the new strand.

Primase

Primase is an enzyme that synthesizes the RNA primer needed for DNA replication. This primer provides the free 3'-hydroxyl group required by DNA polymerase to begin synthesis. Primase lays down a short RNA segment complementary to the DNA template, allowing DNA polymerase to extend the new DNA strand from this starting point.