Enzymes involved in Replication for IIT JAM Biotechnology / GAT B / CUET PG 2025 | Molecular Biology
IIT JAM Biotechnology , GAT B , CUET PG & TIFR・63 minutes read
A lecture series on Molecular Biology is starting, covering topics like DNA replication, DNA polymerase, and cell division mechanisms. The focus is on understanding key processes and preparing for upcoming sessions, including a practice session with Mohit Sir in the evening.
Insights
- DNA replication involves a template-dependent process where DNA polymerase synthesizes in the 5' to 3' direction, removing two phosphates and adding one phosphate, resulting in semi-continuous synthesis.
- Meselson and Stahl's experiment confirmed the semi-conservative nature of DNA replication by using N15 and N14 isotopes, showing that one parental strand remains in each new DNA molecule.
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Recent questions
What is the central dogma?
The central dogma refers to the flow of genetic information from DNA to RNA to protein.
Why is DNA replication important?
DNA replication is crucial for cell division and passing genetic information to offspring.
What are the phases of cell division?
Cell division involves phases like prophase, metaphase, anaphase, and telophase.
What is the role of DNA polymerase?
DNA polymerase is responsible for synthesizing new DNA strands during replication.
What did Meselson and Stahl's experiment prove?
Meselson and Stahl's experiment confirmed the semi-conservative nature of DNA replication.
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Summary
00:00
"Molecular Biology Lecture Series and Practice Session"
- Lecture series on Molecular Biology starting, focusing on complete molecular biology and details.
- Request to like and share the session for study groups.
- Covering basics like central dogma, DNA information, enzymes in replication mechanism.
- Teaching complete biology basics to ensure understanding for upcoming lectures.
- Practice session with Mohit Sir in the evening for topic-related questions.
- Launching exclusive batch for IIT JAM 2025 hopefuls covering Physics, Chemistry, and Maths.
- Discussing DNA replication process, importance of replication for cell division.
- Different phases of prokaryotic and eukaryotic cell division, focusing on S phase for DNA synthesis.
- Similarities and differences in prokaryotic and eukaryotic DNA replication mechanisms.
- Template-dependent process of DNA replication, synthesis direction from 5' to 3' by DNA polymerase.
18:24
DNA Polymerase and Replication Process Overview
- DNA polymerase removes two phosphates
- DNA polymerase removes beta phosphate and adds gamma phosphate
- Nucleotide consists of five prime nucleotide, phosphate, alpha burst, and base
- DNA polymerase removes alpha phosphate
- Semi-continuous process involves continuous synthesis on one strand and discontinuous synthesis on the other
- Replication process results in complete synthesis of one strand and small fragments on the other
- DNA polymerase cannot initiate replication and requires a free three prime end
- Polymerase provides the three prime end for nucleotide addition
- Prokaryotic DNA is circular with a small genome, while eukaryotic DNA is linear with larger genome and nucleosomes
- Prokaryotic replication starts and stops at one locus, while eukaryotic replication has multiple origin sites and can occur simultaneously at different sites
37:17
DNA Replication: Semi-Conservative Nature Confirmed
- The experimental results matched the theoretical measurements.
- A band of light DNA was observed, indicating hybrid DNA.
- The experiment confirmed the completion of the semi-conservative replication process.
- The new isotopes could not integrate into the parental DNA stand.
- Meselson and Stahl's experiment proved the semi-conservative nature of DNA replication.
- The experiment involved DNA synthesis with N15 isotopes and subsequent use of N14 isotopes.
- Conservative replication would create new DNA while maintaining the old stands.
- Semi-conservative replication would result in one old and one new stand.
- The experiment confirmed the semi-conservative mode of DNA replication.
- The process involved various proteins and enzymes like helicase and helicase loader.
55:04
"DNA Polymerase: Key Enzyme in DNA Synthesis"
- Helicase works in two directions: one helicase works in the 5' to 3' direction, while another works in the 3' to 5' direction.
- The leading strand is unwound by helicase, attached to the helicase, and starts unwinding.
- Helicase bound to the lagging strand moves forward, performing incremental unbinding.
- Single-stranded binding proteins maintain DNA strands separate, known as helix destabilizers.
- Single-stranded binding proteins interact with single-stranded DNA to keep them separated.
- DNA polymerase is crucial for DNA synthesis, with different types for prokaryotic and eukaryotic cells.
- DNA polymerase one, discovered by Arthur Kornberg, is a monomeric enzyme with primer removal, gap filling, and proofreading activities.
- DNA polymerase one is involved in nucleotide excision repair and primer removal in prokaryotic cells.
- DNA polymerase two is essential for base excision repair mechanisms.
- DNA polymerase three is a major replicative enzyme with multiple subunits performing polymerization, proofreading, and clamp functions.
01:14:30
DNA Polymerases: Functions and Mechanisms Explained
- Tomorrow's reading will focus on DNA polymerases, specifically polymerases four and five, coded by genes named Din B and yam y2dc respectively.
- DNA polymerase three's details will be discussed in the upcoming lecture, emphasizing its role in the complete mechanism of functioning.
- Prokaryotic DNA polymerases include polymerases 1, 2, 3, fur, and five, with polymerase three being particularly useful in gap removal and filling during DNA repair.
- Eukaryotic DNA polymerases, such as polymerase alpha, beta, gamma, delta, and epsilon, have distinct functions in primer synthesis, base excision repair, mitochondrial DNA replication, and replication of organelle DNA.
- DNA polymerase epsilon and delta are major replicative enzymes in eukaryotic cells, with epsilon synthesizing the leading strand and delta working on the lagging strand.
- Lagging strand synthesis involves DNA polymerase alpha as a primer, beta for base excision repair, gamma for mitochondrial DNA, and epsilon for organelle DNA replication.
- DNA polymerase esin synthesizes the leading strand, while DNA polymerase alpha functions as a primer, and DNA polymerase beta is involved in base excision repair.
- DNA polymerase gamma is crucial for mitochondrial DNA replication, while DNA polymerase delta and epsilon are major replicative enzymes for organelle DNA.
- Topoisomerases, including topoisomerase one and two, are essential for breaking and resealing single and double-stranded DNA ends, with topoisomerase two requiring ATP for its function.
