Questions and Answers
What are the short fragments formed on the lagging strand during DNA replication called?
The lagging strand is synthesized continuously from 5’ to 3’ direction.
False
What enzyme removes the primer sequences during DNA replication?
Exonuclease
Replication is termed semi-conservative because the new DNA consists of one _____ and one _____ chain of nucleotides.
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Which enzyme is responsible for joining the Okazaki fragments together?
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Match the following enzymes with their roles in DNA replication:
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The initiation of DNA replication starts with the attachment of helicase.
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What is the result of DNA replication in terms of the genetic makeup of daughter cells?
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What is the primary component found at replication origins in DNA that makes it easier to unwind?
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Replication in prokaryotes occurs unidirectionally around the circular chromosome.
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How long does it take for E.coli to replicate its genome?
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The __________are responsible for opening up the DNA helix during the initiation of replication.
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Match the following terms with their definitions:
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What is the role of the replisome during DNA replication?
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In prokaryotic DNA replication, the process initiates at multiple origins of replication on circular chromosomes.
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What type of replication model is used during DNA replication?
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What is the primary characteristic of the leading strand during DNA replication?
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Okazaki fragments are exclusively associated with the synthesis of the leading strand.
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What enzyme is responsible for joining Okazaki fragments?
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The process of DNA replication is termed __________ because one original strand is conserved in each new DNA molecule.
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Match the following enzymes with their roles in DNA replication:
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Where does the replication of both prokaryotic and eukaryotic DNA begin?
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Replication forks move away from the origin of replication in opposite directions.
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Name the small, discontinuous pieces of DNA formed on the lagging strand during replication.
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Study Notes
Origin and Initiation of Replication
- A-T rich regions in DNA are easier to separate and typically found at replication origins.
- DNA replication begins at a unique sequence known as the origin of replication, which binds initiator proteins that start the replication process.
- In E. coli, the origin consists of 245 base pairs of DNA where the initiator protein unwinds the DNA.
Bacterial DNA Replication Model
- Circular bacterial chromosomes have a replicator near the replication origin.
- Initiator proteins recruit at the replicator, resulting in melting of the DNA helix and loading of helicase.
- Assembled replisomes replicate DNA bidirectionally, creating two copies of the bacterial chromosome.
Prokaryotic DNA Replication
- Initiation occurs at a single origin of replication, proceeding bidirectionally until complete.
- Two replication forks form, actively mediating the replication process.
Synthesis of Leading and Lagging Strands
- The leading strand is synthesized continuously in the direction of the replication fork.
- The lagging strand is synthesized in segments called Okazaki fragments, which are made backward relative to the replication fork.
Role of Proteins in Initiation
- Helicase and single-stranded DNA-binding proteins unwind and expose the template DNA.
- Primase synthesizes the leading strands, forming two replication forks moving in opposite directions along the circular chromosome.
Lagging Strand Replication
- Numerous primers bind at various points along the lagging strand, initiating the synthesis of Okazaki fragments in the 5' to 3' direction.
- Exonuclease removes primer sequences, and gaps are filled with complementary bases before ligation occurs, creating a continuous DNA strand.
Semi-Conservative Nature of DNA Replication
- DNA replication produces two DNA molecules, each consisting of one new and one original strand, maintaining genetic continuity.
- After replication, DNA coils into a double helix structure.
Triggering Replication
- Initiation of DNA replication involves two steps: the initiator protein unwinds a short stretch of DNA, followed by helicase breaking hydrogen bonds to separate the DNA strands.
- Helicase continues to unwind the double helix, facilitating replication.
Genetic Identity Post-Replication
- Following replication, the cell has double the amount of DNA, allowing for accurate distribution of genetic material into daughter cells, ensuring genetic identity between parent and offspring.
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Description
This quiz explores the origin and initiation of DNA replication, focusing on how A-T rich regions are critical for this process. It also includes a model for bacterial DNA replication initiation, providing insights into circular bacterial chromosomes. Test your understanding of these fundamental concepts in molecular biology.
