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Questions and Answers
What is the primary function of helicase in DNA replication?
What is the primary function of helicase in DNA replication?
Which of the following is a characteristic of the leading strand synthesis?
Which of the following is a characteristic of the leading strand synthesis?
What is the function of DNA polymerase in DNA replication?
What is the function of DNA polymerase in DNA replication?
Which of the following is a characteristic of the lagging strand synthesis?
Which of the following is a characteristic of the lagging strand synthesis?
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What is the role of primase in DNA replication?
What is the role of primase in DNA replication?
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Which enzyme is responsible for joining Okazaki fragments?
Which enzyme is responsible for joining Okazaki fragments?
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During DNA replication, what is the direction of synthesis for the leading strand?
During DNA replication, what is the direction of synthesis for the leading strand?
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What is the final step of DNA replication?
What is the final step of DNA replication?
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What is the purpose of topoisomerase during DNA replication?
What is the purpose of topoisomerase during DNA replication?
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What is the function of single-strand binding proteins (SSBs) during DNA replication?
What is the function of single-strand binding proteins (SSBs) during DNA replication?
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In which direction is the leading strand synthesized?
In which direction is the leading strand synthesized?
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What is the purpose of RNA primers in DNA replication?
What is the purpose of RNA primers in DNA replication?
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What is the purpose of Okazaki fragments in DNA replication?
What is the purpose of Okazaki fragments in DNA replication?
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What is the primary function of DNA ligase during DNA replication?
What is the primary function of DNA ligase during DNA replication?
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What is the purpose of checkpoints in DNA replication?
What is the purpose of checkpoints in DNA replication?
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What is the result of the DNA replication process?
What is the result of the DNA replication process?
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Study Notes
Overview of DNA Replication
DNA replication is the process by which a cell makes an exact copy of its DNA before cell division.
Initiation of DNA Replication
- Unwinding of DNA: The double helix structure of DNA is unwound by an enzyme called helicase.
- Binding of primers: Short RNA molecules called primers bind to the template strands at specific regions called origin of replication.
- Recruitment of enzymes: An enzyme called DNA polymerase is recruited to the replication fork.
Leading Strand Synthesis
- Continuous synthesis: The leading strand is synthesized continuously in the 5' to 3' direction.
- DNA polymerase: The enzyme DNA polymerase reads the template strand and matches the incoming nucleotides to the base pairing rules (A-T and G-C).
- Proofreading and editing: DNA polymerase also proofreads and edits the newly synthesized strand to ensure accuracy.
Lagging Strand Synthesis
- Discontinuous synthesis: The lagging strand is synthesized in short, discontinuous segments called Okazaki fragments.
- RNA primers: Each Okazaki fragment is initiated with an RNA primer.
- DNA polymerase: DNA polymerase synthesizes the Okazaki fragments in the 5' to 3' direction.
- RNA primer removal: The RNA primers are removed and replaced with DNA nucleotides.
- Ligation: The Okazaki fragments are joined together by an enzyme called DNA ligase.
Elongation and Completion
- Elongation: The leading strand and lagging strand are continuously synthesized until the replication fork is reached.
- Completion: The replication process is completed when the replication fork is reached, resulting in two identical copies of DNA.
Key Enzymes Involved in DNA Replication
- Helicase: Unwinds the DNA double helix.
- Primase: Synthesizes RNA primers.
- DNA polymerase: Synthesizes new DNA strands.
- DNA ligase: Joins Okazaki fragments together.
Importance of DNA Replication
- Genetic continuity: Ensures the transmission of genetic information from one generation to the next.
- Cell division: Allows for the production of new cells during growth, development, and tissue repair.
Overview of DNA Replication
- DNA replication is the process by which a cell makes an exact copy of its DNA before cell division.
Initiation of DNA Replication
- Helicase unwinds the double helix structure of DNA.
- Short RNA molecules called primers bind to the template strands at specific regions called origin of replication.
- DNA polymerase is recruited to the replication fork.
Leading Strand Synthesis
- The leading strand is synthesized continuously in the 5' to 3' direction.
- DNA polymerase reads the template strand and matches the incoming nucleotides to the base pairing rules (A-T and G-C).
- DNA polymerase also proofreads and edits the newly synthesized strand to ensure accuracy.
Lagging Strand Synthesis
- The lagging strand is synthesized in short, discontinuous segments called Okazaki fragments.
- Each Okazaki fragment is initiated with an RNA primer.
- DNA polymerase synthesizes the Okazaki fragments in the 5' to 3' direction.
- The RNA primers are removed and replaced with DNA nucleotides.
- The Okazaki fragments are joined together by an enzyme called DNA ligase.
Elongation and Completion
- The leading strand and lagging strand are continuously synthesized until the replication fork is reached.
- The replication process is completed when the replication fork is reached, resulting in two identical copies of DNA.
Key Enzymes Involved in DNA Replication
- Helicase unwinds the DNA double helix.
- Primase synthesizes RNA primers.
- DNA polymerase synthesizes new DNA strands.
- DNA ligase joins Okazaki fragments together.
Importance of DNA Replication
- Ensures the transmission of genetic information from one generation to the next.
- Allows for the production of new cells during growth, development, and tissue repair.
DNA Replication Process
Initiation
- DNA replication begins at a specific region called the origin of replication
- Helicase unwinds the double helix, creating a replication fork
- Topoisomerase relaxes the tension in the DNA molecule as it unwinds
Unwinding and Binding
- Single-strand binding proteins (SSBs) bind to single-stranded DNA to prevent re-annealing
- Primase adds short RNA primers to template strands at specific primer binding sites
Leading Strand Synthesis
- DNA polymerase reads the template strand, matching nucleotides to base pairing rules (A-T, G-C)
- Nucleotides are added to the growing strand, forming a complementary copy of the template strand
- Leading strand is synthesized continuously in the 5' to 3' direction
Lagging Strand Synthesis
- Lagging strand is synthesized in short, discontinuous segments called Okazaki fragments
- Each Okazaki fragment is about 1000-2000 nucleotides long and synthesized in the 5' to 3' direction
- RNA primers are removed, and gaps are filled by DNA polymerase
Elongation and Proofreading
- DNA polymerase continues to synthesize new DNA strands, adding nucleotides to growing strands
- DNA polymerase also proofreads and corrects errors, ensuring high fidelity of replication
Ligation
- DNA ligase seals gaps between Okazaki fragments in the lagging strand
- Resulting molecule is a complete, double-stranded DNA molecule identical to the original DNA
Regulation
- DNA replication is regulated by checkpoints to ensure accurate and complete replication
- Checkpoints can pause or halt replication if errors are detected
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Description
Learn about the process of DNA replication, including initiation, stages, and enzymes involved in creating an exact copy of a cell's DNA.
