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Questions and Answers
What is the primary direction of DNA replication on the leading strand?
What is the function of exonuclease in DNA replication?
What is the purpose of multiple primers on the lagging strand?
What is the result of DNA replication in eukaryotic cells?
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What is the role of DNA polymerase alpha, delta, and epsilon in eukaryotic cells?
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What is the characteristic of the newly formed strand on the leading strand?
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What is the function of DNA ligase in DNA replication?
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What is the characteristic of the replication process on the lagging strand?
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What is the purpose of Okazaki fragments in DNA replication?
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What is the final result of the replication process in eukaryotic cells?
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Study Notes
DNA Replication
- Occurs in all cells to copy DNA and transfer genetic information to daughter cells
- Vital for cell growth, repair, and reproduction in organisms
- Takes place in the nucleus
Semi-Conservative Replication
- Parental strands are not degraded
- Base pairing allows each strand to serve as a template strand
- Replication begins at an origin and usually proceeds bi-directionally
- DNA synthesis proceeds in a 5' - 3' direction and is semi-discontinuous
Enzymes Involved in DNA Replication
- DNA helicase: unwinds and separates double-stranded DNA, forms the replication fork
- DNA primase: generates RNA primers, short RNA molecules that act as templates for DNA replication
- DNA polymerases: synthesize new DNA molecules by adding nucleotides to leading and lagging DNA strands
- Topoisomerase or DNA Grase: unwinds and rewinds DNA strands to prevent tangling or supercoiling
- Exonucleases: remove nucleotide bases from the end of a DNA chain
- DNA ligase: joins DNA fragments together by forming phosphodiester bonds between nucleotides
DNA Replication Steps
Initiation
- Identification of the origins of replication
- Unwinding (denaturation) of dsDNA to provide an SSDNA template
- Formation of the replication fork
Elongation
- Initiation of DNA synthesis and elongation
- DNA polymerases add new base pairs complementary to the strand during replication
- Leading strand: continuous synthesis in the 5' - 3' direction
- Lagging strand: discontinuous synthesis, multiple primers bind, and Okazaki fragments are formed
Termination
- Primer removal by exonuclease
- Ligation of newly synthesized DNA segments by DNA ligase
- Formation of two identical DNA molecules, each with one strand from the parent molecule and one new strand
- The resulting DNA molecules coil into the familiar double helix shape
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Description
Learn about the fundamental process of DNA replication, its importance in cell growth, repair, and reproduction, and how it occurs in the nucleus.
