DNA Replication Study Notes

DNA Replication Study Notes

DNA Polymerase Function

• Responsible for synthesizing new DNA strands by adding nucleotides complementary to the template strand.
• Functions in a 5' to 3' direction, meaning it adds nucleotides to the 3' end of the growing DNA strand.
• Requires a primer with a free 3' hydroxyl group to initiate synthesis.
• Proofreads newly synthesized DNA for errors, enhancing fidelity by removing incorrectly paired nucleotides.

Helicase Role In Unzipping

• Unwinds and separates the double-stranded DNA at the replication fork.
• Breaks hydrogen bonds between complementary bases, allowing the two strands to become accessible for replication.
• Essential for creating single-stranded DNA templates for the synthesis of new strands.

Primase Activity

• Synthesizes short RNA primers that provide a starting point for DNA synthesis.
• The primers are complementary to the template strand and are necessary for DNA polymerase to begin synthesis.
• Functions on both leading and lagging strands, creating a primer for each Okazaki fragment on the lagging strand.

Ligase In Okazaki Fragments

• Joins Okazaki fragments on the lagging strand by forming phosphodiester bonds between adjacent nucleotides.
• Seals nicks in the sugar-phosphate backbone after RNA primers are removed and replaced with DNA.
• Ensures the continuity and integrity of the newly synthesized DNA strand.

Topoisomerase Function

• Relieves the torsional strain and supercoiling ahead of the replication fork caused by unwinding of DNA.
• Cuts one or both strands of DNA to allow for rotation and then reseals the strands.
• Prevents DNA tangling and breakage during the replication process, facilitating smooth progression of helicase and polymerase.

DNA Replication Study Notes

DNA Polymerase Function

• Synthesizes new DNA strands by adding nucleotides that are complementary to the template strand.
• Operates in a 5' to 3' direction, adding nucleotides to the 3' end of the growing strand.
• Requires an RNA primer with a free 3' hydroxyl group to initiate the synthesis process.
• Enhances fidelity by proofreading newly replicated DNA, removing mismatched nucleotides.

Helicase Role in Unzipping

• Unwinds and separates double-stranded DNA at the replication fork to facilitate replication.
• Breaks hydrogen bonds between complementary bases, exposing two strands for new strand synthesis.
• Creates single-stranded DNA templates necessary for DNA polymerase to synthesize new strands.

Primase Activity

• Synthesizes short RNA primers that are essential for initiating DNA synthesis.
• Primers are complementary to the template strand and act as starting points for DNA polymerase.
• Functions on both the leading and lagging strands, generating a primer for each Okazaki fragment on the lagging strand.

Ligase in Okazaki Fragments

• Joins Okazaki fragments on the lagging strand by forming phosphodiester bonds between adjacent nucleotides.
• Seals nicks in the sugar-phosphate backbone once RNA primers are replaced with DNA.
• Ensures the integrity and continuity of the newly synthesized DNA strand.

Topoisomerase Function

• Relieves torsional strain and supercoiling ahead of the replication fork caused by DNA unwinding.
• Cuts one or both strands of DNA, allowing for rotation to relieve tension before resealing the strands.
• Prevents tangling and breakage of DNA during replication, aiding helicase and polymerase movement.