Podcast
Questions and Answers
What model of DNA replication ensures that each newly synthesized strand remains paired with its original template strand?
What model of DNA replication ensures that each newly synthesized strand remains paired with its original template strand?
Which enzyme is responsible for relieving supercoiling during DNA replication?
Which enzyme is responsible for relieving supercoiling during DNA replication?
What happens during the Meselson and Stahl experiment that ruled out conservative replication?
What happens during the Meselson and Stahl experiment that ruled out conservative replication?
How does the origin of replication differ between bacteria and eukaryotes?
How does the origin of replication differ between bacteria and eukaryotes?
Signup and view all the answers
Which of the following roles does primase play in DNA replication?
Which of the following roles does primase play in DNA replication?
Signup and view all the answers
Which protein stabilizes single-stranded DNA after being unwound during replication to prevent reformation of secondary structures?
Which protein stabilizes single-stranded DNA after being unwound during replication to prevent reformation of secondary structures?
Signup and view all the answers
What is the primary role of RNAse H in DNA replication?
What is the primary role of RNAse H in DNA replication?
Signup and view all the answers
What significant outcome is produced by the dispersive model of DNA replication after two cycles?
What significant outcome is produced by the dispersive model of DNA replication after two cycles?
Signup and view all the answers
Study Notes
DNA Replication Overview
- RNA has roles as an information carrier (mRNA) and catalyst (ribosomes).
- DNA replication models include conservative (parental strands always together), semi-conservative (one template strand and one new strand), and dispersive (alternating parent and daughter DNA).
- Meselson and Stahl's experiment proved semi-conservative replication. Conservative and dispersive models were disproven.
Meselson-Stahl Experiment Details
- Experiment ruled out conservative replication due to intermediate density after one cycle.
- Dispersive model was also ruled out after two replication cycles, as intermediate density should have progressively decreased but did not.
Replication Fork and Origins
- Replication fork: Where DNA strands separate during replication.
- Origin of replication: DNA sequence where replication begins on chromosomes/plasmids. This is where DNA unwinds.
Bacterial vs. Eukaryotic Replication
- Bacteria: Uni-directional replication with one origin.
- Eukaryotes: Bi-directional replication with multiple origins.
Enzymes in DNA Replication
-
Helicase:
- Binds to single-stranded DNA (ssDNA) and hydrolyzes ATP to move along the strand.
- Unwinds DNA by displacing the other strand when it encounters double-stranded regions.
- Assembled as a homohexamer with a pore for ssDNA passage.
-
Single-stranded binding proteins (SSBs):
- Straightens DNA to prevent folding, slowing DNA polymerase.
- Presents bases upwards for incoming dNTPs to dock.
-
Topoisomerase:
- Relieves DNA supercoiling, allowing replication to proceed.
- Two classes:
- Topoisomerase I: Creates single-strand breaks.
- Topoisomerase II: Creates double-strand breaks, resealing after unwinding DNA.
-
Primase:
- Initiates replication by joining two NTPs to provide the 3'OH that DNA polymerase requires to extend.
- RNA primer: Approximately 10 nucleotides long.
-
RNAse H:
- Digests most of the RNA primer, but cannot break RNA-DNA bonds.
-
DNA polymerase I:
- Digests the final RNA primer, catalyzing DNA synthesis across the gap.
-
DNA ligase:
- Joins Okazaki fragments.
- Catalyzes the formation of a covalent bond by attacking a phosphate AMP bond on one strand with the 3'OH on the other strand. This releases AMP.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
Explore the fundamentals of DNA replication, including various models and the significant Meselson-Stahl experiment that confirmed semi-conservative replication. Understand the roles of RNA and the differences between bacterial and eukaryotic replication processes. This quiz will help reinforce essential concepts in molecular biology.
