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What is the function of DNA replication?
What is the function of DNA replication?
To transfer genetic information to the daughter cells.
What is the name of the process where one strand of DNA is copied from the parental strand, resulting in two DNA molecules, each containing one original strand and one new complementary strand?
What is the name of the process where one strand of DNA is copied from the parental strand, resulting in two DNA molecules, each containing one original strand and one new complementary strand?
Semi-conservative replication
What phase of the cell cycle does DNA replication occur?
What phase of the cell cycle does DNA replication occur?
S phase
The process of unwinding DNA during replication begins at specific points on the DNA molecule. What are these points called?
The process of unwinding DNA during replication begins at specific points on the DNA molecule. What are these points called?
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What type of base pairs are origins of replication rich in?
What type of base pairs are origins of replication rich in?
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What protein complex recognizes and binds to origins of replication, initiating the local opening and unwinding of the DNA double helix?
What protein complex recognizes and binds to origins of replication, initiating the local opening and unwinding of the DNA double helix?
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What are the DNA segments between any two origins of replication called?
What are the DNA segments between any two origins of replication called?
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What enzyme separates the two DNA strands by breaking the hydrogen bonds between the nitrogenous base pairs, forming replication bubbles?
What enzyme separates the two DNA strands by breaking the hydrogen bonds between the nitrogenous base pairs, forming replication bubbles?
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What type of proteins bind to the single strands of DNA, preventing them from rewinding and stabilizing them?
What type of proteins bind to the single strands of DNA, preventing them from rewinding and stabilizing them?
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What is created due to the action of helicase and SSB proteins?
What is created due to the action of helicase and SSB proteins?
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DNA polymerases can start DNA synthesis "de novo", meaning they can start from scratch.
DNA polymerases can start DNA synthesis "de novo", meaning they can start from scratch.
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What is the name of the short RNA sequence that acts as a primer for DNA synthesis?
What is the name of the short RNA sequence that acts as a primer for DNA synthesis?
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What enzyme synthesizes the RNA primer?
What enzyme synthesizes the RNA primer?
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What strand is synthesized continuously in the 5' to 3' direction, following the replication fork directly?
What strand is synthesized continuously in the 5' to 3' direction, following the replication fork directly?
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Which DNA polymerase synthesizes the leading strand?
Which DNA polymerase synthesizes the leading strand?
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What strand is synthesized discontinuously in the 5' to 3' direction, in short fragments called Okazaki fragments, due to the direction of the replication fork?
What strand is synthesized discontinuously in the 5' to 3' direction, in short fragments called Okazaki fragments, due to the direction of the replication fork?
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What enzymes have proofreading activity, removing mismatched nucleotides from the newly synthesized DNA strand?
What enzymes have proofreading activity, removing mismatched nucleotides from the newly synthesized DNA strand?
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What enzymes remove DNA supercoiling, which arises during DNA replication as the DNA unwinds?
What enzymes remove DNA supercoiling, which arises during DNA replication as the DNA unwinds?
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What type of topoisomerase makes transient breaks in both strands of the DNA molecule, allowing for the strands to rotate around each other, and then reseals these breaks?
What type of topoisomerase makes transient breaks in both strands of the DNA molecule, allowing for the strands to rotate around each other, and then reseals these breaks?
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What type of topoisomerase produces a single-strand break, allowing for the rotation of one strand around the other, and then reseals the break?
What type of topoisomerase produces a single-strand break, allowing for the rotation of one strand around the other, and then reseals the break?
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What enzyme removes the RNA primers from the newly synthesized DNA strand?
What enzyme removes the RNA primers from the newly synthesized DNA strand?
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Which DNA polymerase fills the gaps between Okazaki fragments on the lagging strand?
Which DNA polymerase fills the gaps between Okazaki fragments on the lagging strand?
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What enzyme joins the ends of the adjacent DNA fragments?
What enzyme joins the ends of the adjacent DNA fragments?
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What are the ends of eukaryotic linear chromosomes called?
What are the ends of eukaryotic linear chromosomes called?
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What is the repeating sequence found in telomeres?
What is the repeating sequence found in telomeres?
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Why is the single-stranded region at the end of the lagging strand important?
Why is the single-stranded region at the end of the lagging strand important?
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The leading strand can be synthesized to the end of the parent strand while the lagging strand cannot.
The leading strand can be synthesized to the end of the parent strand while the lagging strand cannot.
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Cellular aging and death occur when the ends of the chromosomes get slightly shorter with each cell division until the telomeres are gone, and DNA is degraded.
Cellular aging and death occur when the ends of the chromosomes get slightly shorter with each cell division until the telomeres are gone, and DNA is degraded.
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What enzyme is responsible for maintaining telomere length in cells that do not age, such as germ-line cells and cancer cells?
What enzyme is responsible for maintaining telomere length in cells that do not age, such as germ-line cells and cancer cells?
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Telomerase is a reverse transcriptase enzyme that can synthesize DNA complementary to the short RNA molecule present in its structure that act as a template.
Telomerase is a reverse transcriptase enzyme that can synthesize DNA complementary to the short RNA molecule present in its structure that act as a template.
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Cells that have differentiated and no longer divide do not express telomerase.
Cells that have differentiated and no longer divide do not express telomerase.
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Cells that do not age, such as germ-line cells and cancer cells, contain telomerase.
Cells that do not age, such as germ-line cells and cancer cells, contain telomerase.
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Telomerase expression is reactivated in tumor cells.
Telomerase expression is reactivated in tumor cells.
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What is the name of the disorder that results from hypersensitivity to sunlight (UV light), leading to increased skin cancer, premature aging, and death?
What is the name of the disorder that results from hypersensitivity to sunlight (UV light), leading to increased skin cancer, premature aging, and death?
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What is the name of the disorder that results from sensitivity to ionizing radiation and certain chemical agents, leading to ataxia, telangiectasia, and an increased risk of cancer?
What is the name of the disorder that results from sensitivity to ionizing radiation and certain chemical agents, leading to ataxia, telangiectasia, and an increased risk of cancer?
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What is the name of the disorder that causes premature aging and retarded growth?
What is the name of the disorder that causes premature aging and retarded growth?
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Study Notes
DNA Synthesis (Replication)
- DNA replication occurs during the S phase of the cell cycle.
- Replication transfers genetic information to daughter cells.
- Replication produces two daughter DNA molecules, each containing one original strand and a new complementary strand (semi-conservative replication).
- Eukaryotic replication involves multiple origins of replication along chromosomes, rich in AT base pairs.
- Origin Recognition Complex (ORC) proteins bind to replication origins to initiate unwinding and opening of the DNA double helix.
- Replicons are the DNA segments between replication origins.
- Multiple origins significantly reduce replication time.
- Helicase enzymes break hydrogen bonds, unwinding DNA into replication bubbles.
- Single-strand binding proteins (SSBs) stabilize the single-stranded DNA, preventing it from rewinding.
- Replication forks are created by helicase and SSB proteins.
Initiation of DNA Synthesis
- DNA synthesis requires RNA primers, as DNA polymerases cannot initiate synthesis from scratch.
- DNA polymerase α-primase complex creates RNA primers.
- The 5'-end of the primer attaches to the 3'-end of the parental strand.
- The 3'-end of the primer accepts the first deoxynucleotide.
Elongation of Leading and Lagging Strands
- DNA polymerases synthesize new strands in the 5' to 3' direction, using the parental strand as a template (3' to 5').
- Leading strand synthesis is continuous in the same direction as the replication fork.
- Lagging strand synthesis is discontinuous, creating short Okazaki fragments in the opposite direction of the replication fork.
- Leading strand synthesis is performed by DNA polymerase ε.
- Lagging strand synthesis is performed by DNA polymerase δ.
Proofreading and Removal of Supercoils
- DNA polymerases have proofreading capabilities to correct errors during synthesis.
- They hydrolytically remove incorrect nucleotides and replace them.
- Topoisomerases alleviate DNA supercoiling during unwinding by making transient breaks in both DNA strands, allowing the untangling of the DNA.
- Topoisomerase I creates a single break.
- Topoisomerase II creates a double break.
Termination and Joining Fragments
- RNAse H removes RNA primers.
- DNA polymerase δ fills the gaps left by the RNA primers.
- DNA ligase joins the Okazaki fragments into a continuous lagging strand.
Telomeres and Telomerase
- Telomeres are the protective caps at the ends of linear chromosomes.
- Telomeres consist of repeated sequences (TTAGGG) that prevent degradation of chromosome ends.
- Telomerase is a reverse transcriptase enzyme that adds telomere sequences to chromosome ends to maintain length and prevent degradation.
DNA Repair
- DNA replication is very accurate with error rates per 30,000 bases, or may be subject to environmental elements and damage.
- Errors that are not corrected can lead to hereditary diseases.
- Repair mechanisms involve recognition of the damage by endonucleases, removal of the damaged portion, repair synthesis, and ligation.
- Examples of hereditary DNA repair disorders include Xeroderma pigmentosum, Ataxia-telangiectasia, and Werner's syndrome.
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Description
Explore the intricate process of DNA replication, which occurs during the S phase of the cell cycle. This quiz covers key concepts like semi-conservative replication, the role of helicase, and the importance of RNA primers in DNA synthesis. Test your understanding of how genetic information is accurately passed to daughter cells!
