Podcast
Questions and Answers
What is the role of the protein DnaA in prokaryotic DNA replication?
What is the role of the protein DnaA in prokaryotic DNA replication?
- It separates DNA strands by hydrolyzing ATP.
- It seals the gaps between Okazaki fragments.
- It synthesizes RNA primers on the lagging strand.
- It recognizes and binds to special sequences known as replication origins. (correct)
DNA replication results in two daughter copies, each containing two strands of newly synthesized DNA.
DNA replication results in two daughter copies, each containing two strands of newly synthesized DNA.
False (B)
What enzyme alleviates the overwinding of DNA caused by the action of helicase?
What enzyme alleviates the overwinding of DNA caused by the action of helicase?
topoisomerase
Okazaki fragments are synthesized on the ______ strand during DNA replication.
Okazaki fragments are synthesized on the ______ strand during DNA replication.
Match the enzyme with its function in DNA replication:
Match the enzyme with its function in DNA replication:
Why are RNA primers necessary for DNA replication?
Why are RNA primers necessary for DNA replication?
DNA polymerase can initiate DNA synthesis without a primer.
DNA polymerase can initiate DNA synthesis without a primer.
What is the function of single-strand binding protein (SSB) in DNA replication?
What is the function of single-strand binding protein (SSB) in DNA replication?
The enzyme that joins Okazaki fragments together is called ______.
The enzyme that joins Okazaki fragments together is called ______.
What does the term 'processivity' refer to in the context of DNA polymerase?
What does the term 'processivity' refer to in the context of DNA polymerase?
The leading strand is synthesized in the 3'-to-5' direction.
The leading strand is synthesized in the 3'-to-5' direction.
What is the role of telomerase in eukaryotic cells?
What is the role of telomerase in eukaryotic cells?
The accessory protein that helps secure DNA polymerase to the template is called the sliding DNA ______.
The accessory protein that helps secure DNA polymerase to the template is called the sliding DNA ______.
Which activity does DNA polymerase possess that allows it to remove incorrect nucleotides?
Which activity does DNA polymerase possess that allows it to remove incorrect nucleotides?
Telomeres are made up of repeats of a five-nucleotide motif.
Telomeres are made up of repeats of a five-nucleotide motif.
If DNA replication were to proceed without topoisomerases, what would be the most likely consequence?
If DNA replication were to proceed without topoisomerases, what would be the most likely consequence?
What is the direction of the exonuclease activity of DNA polymerase that allows for proofreading?
What is the direction of the exonuclease activity of DNA polymerase that allows for proofreading?
The 'bubble' of denatured DNA created by DnaA at the replication origin is essential for the recruitment of ______.
The 'bubble' of denatured DNA created by DnaA at the replication origin is essential for the recruitment of ______.
Which of the following is NOT directly involved in preventing the reannealing of separated DNA strands during replication?
Which of the following is NOT directly involved in preventing the reannealing of separated DNA strands during replication?
Eukaryotic DNA replication can replicate the few nucleotides at the 3' ends of the template strand since RNA primers at those positions can be replaced by DNA.
Eukaryotic DNA replication can replicate the few nucleotides at the 3' ends of the template strand since RNA primers at those positions can be replaced by DNA.
What molecule, hydrolyzed by ligase, provides the energy to create phosphodiester bonds between DNA fragments?
What molecule, hydrolyzed by ligase, provides the energy to create phosphodiester bonds between DNA fragments?
Although seemingly contradicotory, DNA polymerase extends primers in the 5'-to-3' direction, and the lagging strand is synthesized in fragments approximately every ______ nucleotides
Although seemingly contradicotory, DNA polymerase extends primers in the 5'-to-3' direction, and the lagging strand is synthesized in fragments approximately every ______ nucleotides
Telomerase utilizes which of the following to extend telomeres?
Telomerase utilizes which of the following to extend telomeres?
If a cell were deficient in DNA ligase, what would be the most immediate consequence on DNA replication?
If a cell were deficient in DNA ligase, what would be the most immediate consequence on DNA replication?
DNA polymerase I is solely responsible for the extension of both the leading and lagging strands during DNA replication.
DNA polymerase I is solely responsible for the extension of both the leading and lagging strands during DNA replication.
Flashcards
Semiconservative Replication
Semiconservative Replication
Each new DNA molecule contains one original and one newly synthesized strand.
Replication Origins
Replication Origins
In prokaryotes, DNA replication starts at specific sequences called replication origins.
DnaA Function
DnaA Function
DnaA initiates replication by binding to the replication origin, causing DNA to denature and form a bubble.
DnaB (Helicase)
DnaB (Helicase)
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SSB Function
SSB Function
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Topoisomerase Function
Topoisomerase Function
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RNA Primase
RNA Primase
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DNA Polymerase Function
DNA Polymerase Function
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Exonuclease Activity
Exonuclease Activity
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Leading Strand
Leading Strand
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Lagging Strand
Lagging Strand
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Okazaki Fragments
Okazaki Fragments
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DNA Ligase
DNA Ligase
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Processivity
Processivity
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Sliding DNA Clamp
Sliding DNA Clamp
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Telomeres
Telomeres
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Telomerase Function
Telomerase Function
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Study Notes
- Daughter DNA copies contain one strand of the original DNA
- Prokaryotic DNA replication starts with DnaA protein recognizing genome sequences known as replication origins
- DnaA binding deforms the double helix, creating a small bubble of denatured DNA
- DnaA recruits DnaB (helicase) to the replication origin
- DnaB separates strands using ATP hydrolysis
- Single-strand binding protein (SSB) prevents single-stranded DNA from reannealing
- DnaB opening the double helix causes overwinding
- Topoisomerases relieve overwinding by cleaving one strand, unwinding DNA, and religating the strand
- After DNA separation, RNA primase creates complementary RNA primers using DNA as the template
- DNA polymerase extends RNA primers, it can only extend an existing chain at its 3'-OH end by adding deoxyribonucleotide to the 3'-OH based on a template sequence
- Some DNA polymerases have exonuclease activities to remove incorrect nucleotides at the 3' end
- Complementary strands for both original template strands are created simultaneously
- The leading strand is created continuously in the 5' to 3' direction
- The lagging strand extends in the 3'-to-5' direction in fragments known as Okazaki fragments
- Primase creates primers for the lagging strand approximately every 1000 nucleotides
- DNA polymerase extends these primers in a direction pointing away from the replication complex (5'-to-3') until it reaches another RNA primer
- RNA primers are then removed and replaced by DNA
- Ligase connects all fragments through phosphodiester bonds, using ATP hydrolysis
- Processivity of DNA polymerase is its ability to extend the chain without interruption
- Sliding DNA clamp secures DNA polymerase to the template by enclosing the DNA in a protein ring, increasing processivity
- Eukaryotic genomes are linear molecules, making it so the few nucleotides at the 3' ends of the template strand cannot be replicated, resulting in DNA molecules shortening with each replication
- Eukaryotes have telomeres at the end of the chromosome which are repeats of a six nucleotide motif
- Telomerase extends telomeres using an internal RNA template
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