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Questions and Answers
What is the primary function of helicase in DNA replication?
Which of the following is a characteristic of the leading strand synthesis?
What is the function of DNA polymerase in DNA replication?
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?
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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?
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What is the final step of DNA replication?
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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?
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In which direction is the leading strand synthesized?
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What is the purpose of RNA primers in DNA replication?
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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?
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What is the purpose of checkpoints in DNA replication?
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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.
