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Questions and Answers
What type of DNA strand is synthesized continuously towards the replication fork?
What type of DNA strand is synthesized continuously towards the replication fork?
What is the primary reason for the discontinuous synthesis of one of the DNA strands?
What is the primary reason for the discontinuous synthesis of one of the DNA strands?
What are the small segments synthesized on the lagging strand called?
What are the small segments synthesized on the lagging strand called?
What enzyme is responsible for joining Okazaki fragments into a continuous strand?
What enzyme is responsible for joining Okazaki fragments into a continuous strand?
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How is the initiation of each fragment on the lagging strand accomplished?
How is the initiation of each fragment on the lagging strand accomplished?
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What term is given to the process of DNA replication where one strand is continuous and the other is not?
What term is given to the process of DNA replication where one strand is continuous and the other is not?
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Which part of the Okazaki fragments grows toward the previously synthesized fragment?
Which part of the Okazaki fragments grows toward the previously synthesized fragment?
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What key role does primase play in DNA replication?
What key role does primase play in DNA replication?
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What is a characteristic of the β-globin locus in erythroid cells during S phase?
What is a characteristic of the β-globin locus in erythroid cells during S phase?
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What is the core element of an ARS (autonomous replicating sequence)?
What is the core element of an ARS (autonomous replicating sequence)?
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How does the timing of replication initiation differ between cells with shorter and longer cell cycles?
How does the timing of replication initiation differ between cells with shorter and longer cell cycles?
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What is the function of the origin recognition complex (ORC) in eukaryotic cells?
What is the function of the origin recognition complex (ORC) in eukaryotic cells?
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What ensures that each portion of the genome is replicated once during a cell cycle?
What ensures that each portion of the genome is replicated once during a cell cycle?
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What factors influence the selection of sites for the initiation of replication?
What factors influence the selection of sites for the initiation of replication?
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Which statement describes the behavior of the ORC protein complex in yeast cells?
Which statement describes the behavior of the ORC protein complex in yeast cells?
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In vertebrates, how is replication initiation different compared to yeast?
In vertebrates, how is replication initiation different compared to yeast?
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What is the primary function of DnaB in E. coli?
What is the primary function of DnaB in E. coli?
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Which eukaryotic protein serves a similar function to DnaC in E. coli?
Which eukaryotic protein serves a similar function to DnaC in E. coli?
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What is the role of SSB in E. coli replication?
What is the role of SSB in E. coli replication?
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Which enzyme acts as a clamp loader in eukaryotic DNA replication?
Which enzyme acts as a clamp loader in eukaryotic DNA replication?
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Which statement is true about eukaryotic polymerases in comparison to bacterial polymerases?
Which statement is true about eukaryotic polymerases in comparison to bacterial polymerases?
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What is the function of the β clamp in E. coli?
What is the function of the β clamp in E. coli?
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What primarily influences the transcriptional state of a cell?
What primarily influences the transcriptional state of a cell?
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How do DNA polymerases ensure high fidelity during DNA replication?
How do DNA polymerases ensure high fidelity during DNA replication?
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Replication forks are localized at which specific sites within the cell nucleus?
Replication forks are localized at which specific sites within the cell nucleus?
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How are DNA methylation patterns transmitted during cell division?
How are DNA methylation patterns transmitted during cell division?
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What is one reason that DNA repair is more complex in eukaryotic cells compared to prokaryotic cells?
What is one reason that DNA repair is more complex in eukaryotic cells compared to prokaryotic cells?
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Which of the following describes how damaged DNA is often repaired?
Which of the following describes how damaged DNA is often repaired?
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What role do modifications on old histones play in chromatin inheritance?
What role do modifications on old histones play in chromatin inheritance?
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Which enzyme is responsible for directly repairing damage caused by certain alkylating agents in humans?
Which enzyme is responsible for directly repairing damage caused by certain alkylating agents in humans?
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What mechanism allows the complementary strand of DNA to aid in repair?
What mechanism allows the complementary strand of DNA to aid in repair?
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What is the defining characteristic of epigenetic information?
What is the defining characteristic of epigenetic information?
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What is one major difference in DNA replication between E.coli and eukaryotic cells?
What is one major difference in DNA replication between E.coli and eukaryotic cells?
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What role does the RNA primer play in DNA synthesis?
What role does the RNA primer play in DNA synthesis?
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Why is the study of replication in eukaryotic cells considered more complex than in bacteria?
Why is the study of replication in eukaryotic cells considered more complex than in bacteria?
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Which experimental system has been important for studying eukaryotic DNA replication?
Which experimental system has been important for studying eukaryotic DNA replication?
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How does the rate of nucleotide incorporation by eukaryotic polymerases compare to that of E.coli?
How does the rate of nucleotide incorporation by eukaryotic polymerases compare to that of E.coli?
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What is the approximate time it takes for E.coli to complete its DNA replication?
What is the approximate time it takes for E.coli to complete its DNA replication?
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What happens to RNA primers during the DNA synthesis process?
What happens to RNA primers during the DNA synthesis process?
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What common characteristic do archaeal and eukaryotic replication proteins share?
What common characteristic do archaeal and eukaryotic replication proteins share?
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Study Notes
DNA Replication
- DNA replication occurs in a semi-discontinuous manner, meaning one strand is replicated continuously (leading strand) and the other discontinuously (lagging strand).
- The lagging strand is synthesized in small fragments called Okazaki fragments, about 1000 to 2000 nucleotides long.
- Okazaki fragments are joined together by DNA ligase.
- DNA synthesis is initiated by a primase enzyme, which creates a short RNA primer initiating the process.
- E. coli replicates its DNA in approximately 40 minutes, but a new round can begin before the previous one is completed.
Eukaryotic Replication
- Eukaryotic cells have large genomes and complex chromosomal structures, making eukaryotic replication more complex than prokaryotic replication.
- Eukaryotic replication is studied using mutant yeast and animal cells, archaeal species, and in vitro systems, including Xenopus frog egg extracts.
- Eukaryotic DNA replication initiates at multiple origins, unlike prokaryotic replication.
- Replication origins in yeast contain conserved sequences called autonomous replicating sequences (ARSs), which are recognized by the origin recognition complex (ORC).
Replication Control
- Each portion of the genome is replicated only once per cell cycle.
- The initiation of replication requires the origin to pass through several distinct states.
- The ORC protein complex plays a significant role in binding essential proteins required for subsequent steps in replication.
- The selection of sites for initiation of replication is governed by local epigenetic factors such as nucleosome positions, histone modifications, DNA methylation, and transcription levels.
Eukaryotic Replication Proteins
- Eukaryotic DNA polymerases function similarly to bacterial polymerases, synthesizing DNA strands in the 5' → 3' direction.
- Eukaryotic DNA polymerases δ and ɛ are the primary replicating enzymes, synthesizing both the leading strand and Okazaki fragments.
- Eukaryotic DNA polymerase α synthesizes short DNA oligonucleotides as part of the RNA-DNA primer.
- Eukaryotic replication occurs within localized sites called replication foci.
Epigenetic Inheritance
- Epigenetic information that is not encoded within a chromosome's DNA sequence is crucial for cellular functions.
- DNA methylation patterns are transmitted through the DNA methyltransferase DNMT1, which uses the parental DNA strand as a template.
DNA Repair
- Both prokaryotic and eukaryotic cells possess DNA repair mechanisms involving a range of proteins that detect and repair DNA damage.
- DNA damage can be repaired directly or by excising the damaged section, using the complementary strand as a template for reconstruction.
- DNA repair in eukaryotes involves chromatin-reshaping machines such as histone-modifying enzymes and nucleosome remodeling complexes.
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Description
Test your knowledge on DNA replication, including the differences between prokaryotic and eukaryotic processes. This quiz covers key concepts such as leading and lagging strands, Okazaki fragments, and the role of enzymes like primase and DNA ligase. Perfect for students studying molecular biology or genetics.
