1. The document discusses models of homologous recombination including the Holliday model and the double-strand break repair model. It describes the key steps and proteins involved in each model.
2. Recombination involves the breakage and rejoining of DNA. In eukaryotes, the MRN/X complex processes DNA breaks. The Rad51 and Rad54 proteins then facilitate strand invasion and D-loop formation during homologous pairing.
3. Homologous recombination proteins from bacteria and eukaryotes catalyze different steps of the process. In E. coli, RecBCD introduces breaks and generates single strands for RecA to perform strand exchange, while RuvAB and Ruv
This document discusses molecular genetics topics including sex determination, genetic recombination, and transposons. It outlines four units of study: 1) Sex determination and dosage compensation, 2) Genetic recombination mechanisms and models, 3) Enzymes involved in homologous and site-specific recombination, and 4) Bacterial and eukaryotic transposons. The second section provides detailed descriptions of homologous recombination models including Holliday, Whitehouse, Meselson-Radding, and double-strand break repair pathways. Key enzymes in E. coli recombination such as RecBCD, RecA, RuvAB, and RuvC are also summarized.
Recombination in repair n damage of DNA.pptxANAKHA JACOB
• Maintaining a low mutation rate is essential for cell viability and health. It is estimated that both in prokaryotic and eukaryotic cells, DNA is replicated with very high fidelity with one wrong nucleotide incorporated once per 108–1010 nucleotides polymerized. The fidelity of DNA replication relies on nucleotide selectivity of replicative DNA polymerase, exonucleolytic proofreading, and post-replicative DNA repair systems.
• Mutations can occur due to errors in DNA replication as well as due to certain damages to the DNA. Errors in replication are corrected to a great extent by proofreading mechanisms. Maintaining the genetic stability that an organism needs for its survival requires not only an extremely accurate mechanism for replicating DNA but also mechanisms for repairing many accidental lesions that occur continually. Most such spontaneous changes in DNA are temporary because they are immediately corrected by a set of processes that are collectively called DNA repair.• Maintaining a low mutation rate is essential for cell viability and health. It is estimated that both in prokaryotic and eukaryotic cells, DNA is replicated with very high fidelity with one wrong nucleotide incorporated once per 108–1010 nucleotides polymerized. The fidelity of DNA replication relies on nucleotide selectivity of replicative DNA polymerase, exonucleolytic proofreading, and post-replicative DNA repair systems.
• Mutations can occur due to errors in DNA replication as well as due to certain damages to the DNA. Errors in replication are corrected to a great extent by proofreading mechanisms. Maintaining the genetic stability that an organism needs for its survival requires not only an extremely accurate mechanism for replicating DNA but also mechanisms for repairing many accidental lesions that occur continually. Most such spontaneous changes in DNA are temporary because they are immediately corrected by a set of processes that are collectively called DNA repair.• Maintaining a low mutation rate is essential for cell viability and health. It is estimated that both in prokaryotic and eukaryotic cells, DNA is replicated with very high fidelity with one wrong nucleotide incorporated once per 108–1010 nucleotides polymerized. The fidelity of DNA replication relies on nucleotide selectivity of replicative DNA polymerase, exonucleolytic proofreading, and post-replicative DNA repair systems.
• Mutations can occur due to errors in DNA replication as well as due to certain damages to the DNA. Errors in replication are corrected to a great extent by proofreading mechanisms. Maintaining the genetic stability that an organism needs for its survival requires not only an extremely accurate mechanism for replicating DNA but also mechanisms for repairing many accidental lesions that occur continually. Most such spontaneous changes in DNA are temporary because they are immediately corrected by a set of processes that are collectively called DNA repair.
Enzymes involved in homologous recombination.pdfsoniaangeline
1. Key enzymes involved in homologous recombination in E. coli include RecBCD, RecA, RuvA, RuvB, and RuvC. RecBCD and RecA help initiate recombination by processing DNA and catalyzing strand exchange. RuvA, RuvB, and RuvC resolve Holliday junction intermediates through branch migration and resolution.
2. In eukaryotes, meiotic recombination involves Spo11, which introduces DNA double-strand breaks to initiate recombination. The MRX complex then resects the 5' strands, removing Spo11. Rad51 and Dmc1 catalyze strand invasion and exchange between homologs. Rad52 promotes Rad51 fil
This document summarizes homologous recombination in eukaryotes and bacteria. In eukaryotes, homologous recombination repairs double-strand DNA breaks through either the double-strand break repair (DSBR) pathway or synthesis-dependent strand annealing (SDSA) pathway. The DSBR pathway forms double Holliday junctions that are resolved to result in crossover or non-crossover products. In bacteria, the RecBCD pathway repairs double-strand breaks and the RecF pathway repairs single-strand gaps. Both pathways involve strand invasion and branch migration to facilitate homologous recombination.
Replication:
DNA replication is the biological process of producing two identical copies of DNA from the original/parentral DNA molecule.
This process occurs in all living organism.
Basis for biological inheritance
DNA Replication Is Semiconservative
Replication Begins at an Origin and Usually Proceeds Bidirectionally
DNA Synthesis Proceeds in a 5’-3’ Direction and Is semidiscontinuous
DNA replication in eukaryotes involves three main stages: initiation, elongation, and termination. Initiation begins at origins of replication, where the pre-replication complex forms. During elongation, DNA polymerase adds nucleotides to grow new DNA strands by copying existing template strands. Elongation of the leading strand is continuous while the lagging strand occurs in fragments called Okazaki fragments. Termination occurs when the replication forks meet, and the DNA strands are fully replicated. Telomeres protect chromosome ends during replication to prevent shortening with each cell division.
1. The document discusses models of homologous recombination including the Holliday model and the double-strand break repair model. It describes the key steps and proteins involved in each model.
2. Recombination involves the breakage and rejoining of DNA. In eukaryotes, the MRN/X complex processes DNA breaks. The Rad51 and Rad54 proteins then facilitate strand invasion and D-loop formation during homologous pairing.
3. Homologous recombination proteins from bacteria and eukaryotes catalyze different steps of the process. In E. coli, RecBCD introduces breaks and generates single strands for RecA to perform strand exchange, while RuvAB and Ruv
This document discusses molecular genetics topics including sex determination, genetic recombination, and transposons. It outlines four units of study: 1) Sex determination and dosage compensation, 2) Genetic recombination mechanisms and models, 3) Enzymes involved in homologous and site-specific recombination, and 4) Bacterial and eukaryotic transposons. The second section provides detailed descriptions of homologous recombination models including Holliday, Whitehouse, Meselson-Radding, and double-strand break repair pathways. Key enzymes in E. coli recombination such as RecBCD, RecA, RuvAB, and RuvC are also summarized.
Recombination in repair n damage of DNA.pptxANAKHA JACOB
• Maintaining a low mutation rate is essential for cell viability and health. It is estimated that both in prokaryotic and eukaryotic cells, DNA is replicated with very high fidelity with one wrong nucleotide incorporated once per 108–1010 nucleotides polymerized. The fidelity of DNA replication relies on nucleotide selectivity of replicative DNA polymerase, exonucleolytic proofreading, and post-replicative DNA repair systems.
• Mutations can occur due to errors in DNA replication as well as due to certain damages to the DNA. Errors in replication are corrected to a great extent by proofreading mechanisms. Maintaining the genetic stability that an organism needs for its survival requires not only an extremely accurate mechanism for replicating DNA but also mechanisms for repairing many accidental lesions that occur continually. Most such spontaneous changes in DNA are temporary because they are immediately corrected by a set of processes that are collectively called DNA repair.• Maintaining a low mutation rate is essential for cell viability and health. It is estimated that both in prokaryotic and eukaryotic cells, DNA is replicated with very high fidelity with one wrong nucleotide incorporated once per 108–1010 nucleotides polymerized. The fidelity of DNA replication relies on nucleotide selectivity of replicative DNA polymerase, exonucleolytic proofreading, and post-replicative DNA repair systems.
• Mutations can occur due to errors in DNA replication as well as due to certain damages to the DNA. Errors in replication are corrected to a great extent by proofreading mechanisms. Maintaining the genetic stability that an organism needs for its survival requires not only an extremely accurate mechanism for replicating DNA but also mechanisms for repairing many accidental lesions that occur continually. Most such spontaneous changes in DNA are temporary because they are immediately corrected by a set of processes that are collectively called DNA repair.• Maintaining a low mutation rate is essential for cell viability and health. It is estimated that both in prokaryotic and eukaryotic cells, DNA is replicated with very high fidelity with one wrong nucleotide incorporated once per 108–1010 nucleotides polymerized. The fidelity of DNA replication relies on nucleotide selectivity of replicative DNA polymerase, exonucleolytic proofreading, and post-replicative DNA repair systems.
• Mutations can occur due to errors in DNA replication as well as due to certain damages to the DNA. Errors in replication are corrected to a great extent by proofreading mechanisms. Maintaining the genetic stability that an organism needs for its survival requires not only an extremely accurate mechanism for replicating DNA but also mechanisms for repairing many accidental lesions that occur continually. Most such spontaneous changes in DNA are temporary because they are immediately corrected by a set of processes that are collectively called DNA repair.
Enzymes involved in homologous recombination.pdfsoniaangeline
1. Key enzymes involved in homologous recombination in E. coli include RecBCD, RecA, RuvA, RuvB, and RuvC. RecBCD and RecA help initiate recombination by processing DNA and catalyzing strand exchange. RuvA, RuvB, and RuvC resolve Holliday junction intermediates through branch migration and resolution.
2. In eukaryotes, meiotic recombination involves Spo11, which introduces DNA double-strand breaks to initiate recombination. The MRX complex then resects the 5' strands, removing Spo11. Rad51 and Dmc1 catalyze strand invasion and exchange between homologs. Rad52 promotes Rad51 fil
This document summarizes homologous recombination in eukaryotes and bacteria. In eukaryotes, homologous recombination repairs double-strand DNA breaks through either the double-strand break repair (DSBR) pathway or synthesis-dependent strand annealing (SDSA) pathway. The DSBR pathway forms double Holliday junctions that are resolved to result in crossover or non-crossover products. In bacteria, the RecBCD pathway repairs double-strand breaks and the RecF pathway repairs single-strand gaps. Both pathways involve strand invasion and branch migration to facilitate homologous recombination.
Replication:
DNA replication is the biological process of producing two identical copies of DNA from the original/parentral DNA molecule.
This process occurs in all living organism.
Basis for biological inheritance
DNA Replication Is Semiconservative
Replication Begins at an Origin and Usually Proceeds Bidirectionally
DNA Synthesis Proceeds in a 5’-3’ Direction and Is semidiscontinuous
DNA replication in eukaryotes involves three main stages: initiation, elongation, and termination. Initiation begins at origins of replication, where the pre-replication complex forms. During elongation, DNA polymerase adds nucleotides to grow new DNA strands by copying existing template strands. Elongation of the leading strand is continuous while the lagging strand occurs in fragments called Okazaki fragments. Termination occurs when the replication forks meet, and the DNA strands are fully replicated. Telomeres protect chromosome ends during replication to prevent shortening with each cell division.
DNA replication is the process by which a cell makes an identical copy of its DNA. There are three main models of replication: semi-conservative, conservative, and dispersive. Semi-conservative replication results in two identical DNA molecules each with one old and one new strand. DNA polymerases are involved in replicating DNA. The replication process involves initiation, elongation, and termination phases. Initiation begins at origins of replication and results in unwinding of the DNA helix. Elongation involves continuous synthesis of the leading strand and discontinuous synthesis of the lagging strand in short sections called Okazaki fragments. Termination occurs at specific sequences and ensures replication is complete.
1. The document discusses microbial genetics and the flow of genetic information. It defines key terms like genetics, genes, genome, genotype, and phenotype.
2. It describes the structure of DNA and how it carries genetic information as a double-stranded molecule made up of nucleotides. DNA replication is semi-conservative and involves unwinding the strands, creating an RNA primer, and synthesizing new strands in the 5' to 3' direction.
3. The process of transcription is described, where RNA polymerase reads the genetic code from DNA and synthesizes mRNA, which is then translated to produce proteins. Both prokaryotes and eukaryotes undergo transcription but differ in initiation, processing, and coupling with
DNA replication involves the formation of a molecule complementary in shape and this, in
turn, would serve as a template to make a replica of the original molecule.
• Chromosomal DNA replication occurs only during the S phase of the cell cycle.
• In eukaryotes, every base pair in each chromosome be replicated once and only once each
time a cell divides.
• The combination of all the proteins that function at the replication fork is referred to as
the replisome.
The document summarizes DNA replication. It describes that DNA replication produces two identical copies of DNA from one original molecule through a semi-conservative process. This involves unwinding of DNA at origins of replication by helicase to form replication forks that grow bidirectionally. DNA polymerase then synthesizes new strands using the original strands as templates. Replication occurs through initiation, elongation, and termination steps mediated by various proteins at the replication fork. The Meselson-Stahl experiment provided evidence that DNA replication is semi-conservative through density gradient centrifugation of parental and progeny DNA.
DNA replication is the process whereby a cell makes an identical copy of its DNA before cell division. It ensures faithful inheritance of genetic material during cell division. DNA replication is semi-conservative and bidirectional, occurring simultaneously on both strands of the DNA double helix to produce two identical copies. It involves unwinding of the DNA double helix by helicase, synthesis of new strands by DNA polymerases along leading and lagging strands using existing strands as templates, and ligation of fragments by DNA ligase. DNA replication is tightly regulated during the S phase of the cell cycle and is essential for accurate transmission of genetic information from parent to daughter cells.
DNA recombination mechanisms are involved in DNA repair, replication, gene expression and chromosome segregation. Recombination involves the breakage and joining of DNA strands. There are three main classes of recombination: homologous recombination between similar DNA sequences, site-specific recombination occurring at particular DNA sequences, and DNA transposition where segments of DNA move to new locations. Recombination is mediated by enzymes and involves steps like strand exchange, branch migration and resolution of Holliday junction structures to produce recombinant DNA products.
Prokaryotic DNA replication : These slides contains basics of the prokaryotic DNA replication for S.Y.B.Sc and T.Y.B.Sc students of Microbiology and biotechnology
It covers topics like Enzymes used in replication, Semiconservative replication, Meselson and Stahl experiment, Termination of replication, modes of replication: theta and rolling circle, basic rules of replication
DNA replication is the process by which DNA copies itself for cell division. It is semi-conservative, starting at the origin and proceeding bidirectionally. The leading strand is synthesized continuously while the lagging strand is synthesized discontinuously in fragments called Okazaki fragments. RNA primers are required for initiation. DNA polymerase adds nucleotides to the 3' end of the growing strand based on complementary base pairing. Topoisomerases relieve torsional strain from unwinding. DNA ligase seals fragments on the lagging strand. Replication terminates when forks meet on the opposite side of circular DNA in prokaryotes.
Recombinant DNA technology involves combining DNA from different sources and introducing it into a host cell. This allows for precise genetic analysis and practical applications. Key developments included elucidating DNA structure, cracking the genetic code, and describing transcription and translation. Gene cloning was developed in the 1970s, enabling previously impossible experiments. It involves isolating DNA, cutting it with restriction enzymes, ligating it into a vector, transforming host cells to amplify the recombinant DNA. The polymerase chain reaction (PCR) allows amplifying specific DNA regions without living cells by repeated heating and cooling in a test tube. It has revolutionized research fields like genetics and molecular biology.
DNA was discovered in 1868 and carries genetic traits. It is a double-stranded molecule composed of nucleotides that code for inherited characteristics. DNA replication is the process where DNA copies itself during cell division. It occurs in three main steps - initiation, elongation, and proofreading. DNA recombination and mutation can result in changes to the DNA sequence, altering traits or introducing variation. Recombinant DNA techniques cut and join DNA from different sources to produce modified sequences.
The document discusses three models of DNA replication:
1) Asymmetric replication - the leading and lagging strands are replicated differently due to the 5' to 3' directionality of DNA polymerase. The leading strand replicates continuously while the lagging strand replicates discontinuously in short Okazaki fragments.
2) D-loop model - replication in mitochondria where one strand is displaced to form a D-loop and replicates first before the other strand.
3) Rolling circle model - used by plasmids and viruses where one strand is nicked and displaced to be used as a template, forming multiple copies linked together in a concatemer.
Recombination is a fundamental genetic process that occursghorbian20
1. Homologous recombination and site-specific recombination are essential DNA repair and genetic diversity mechanisms. Homologous recombination occurs between similar DNA sequences during meiosis and mitosis, while site-specific recombination involves cleavage and rejoining between specific DNA sites.
2. Double-strand breaks initiate homologous recombination through end resection, strand invasion, and formation of Holliday junctions. These junctions are resolved to form crossover or non-crossover products.
3. Specialized systems, like lambda integration and yeast mating type switching, utilize site-specific recombinases that catalyze recombination between specific DNA sequences.
Able to define replication in the context of the central dogma.
Able to understand the basic mechanism of DNA replication and know the various enzymes that play a role in this process.
Able to know proofreading and repair mechanisms of DNA replications
This document discusses nucleotides, nucleic acids, and heredity. It begins by explaining that cells contain thousands of proteins and chromosomes carry hereditary information in genes made of DNA and histone proteins. The document then discusses that DNA carries genetic information in genes and each gene controls one protein. It describes the basic components and structures of nucleic acids DNA and RNA, including nucleotides, bases, nucleosides, and primary and secondary structures. It explains how DNA replicates and is amplified through PCR. The roles of different RNA types and protein synthesis are covered. The document concludes by discussing DNA repair through the base excision repair pathway.
DNA replication involves separating the two strands of the DNA double helix to serve as templates for producing two new DNA molecules. Each new molecule contains one old strand and one newly synthesized strand. This process of semiconservative replication ensures that each cell receives a complete copy of the genome upon division. DNA polymerases are the key enzymes that catalyze DNA replication by adding nucleotides to the 3' end of a growing DNA strand in a 5' to 3' direction. Replication occurs bidirectionally from an origin of replication.
The nucleotide structure ,consists of
the nitrogenous base ,attached to the 1’ carbon of deoxyribose
,
the phosphate group attached to the 5’ carbon of deoxyribose
,
a free hydroxyl group (-OH) ,at the 3’ carbon of deoxyribose,1. DNA HELICASES,
to separate the strand,
2. GYRASE (Topoisomerases),
unwind the supercoil,
3. Single strand binding protein (SSBP)
, activity of helicase,
keep two strand separate,
protect DNA from nuclease degradation,
release after replication,
DNA replication is a highly regulated process that exactly duplicates the genome during cell division. It involves unwinding of the DNA double helix at the origin of replication by helicase. Each single-stranded template is then used to synthesize a new complementary strand in the 5'-to-3' direction by DNA polymerase. The leading strand is replicated continuously while the lagging strand is replicated discontinuously in short segments called Okazaki fragments that are later joined by ligase. Several proteins and enzymes work together in a coordinated manner to ensure the genome is accurately duplicated and inherited by daughter cells.
DNA replication is a highly regulated process that occurs semiconservatively before cell division. It involves unwinding of the DNA double helix by helicases, followed by synthesis of new strands complementary to each parental strand. This is carried out by DNA polymerases that add nucleotides according to base pairing rules. In eukaryotes, the lagging strand is synthesized discontinuously in fragments called Okazaki fragments which are later joined by DNA ligase. DNA replication ensures faithful transmission of genetic material to daughter cells.
DNA replication is the process by which a cell makes an identical copy of its DNA. There are three main models of replication: semi-conservative, conservative, and dispersive. Semi-conservative replication results in two identical DNA molecules each with one old and one new strand. DNA polymerases are involved in replicating DNA. The replication process involves initiation, elongation, and termination phases. Initiation begins at origins of replication and results in unwinding of the DNA helix. Elongation involves continuous synthesis of the leading strand and discontinuous synthesis of the lagging strand in short sections called Okazaki fragments. Termination occurs at specific sequences and ensures replication is complete.
1. The document discusses microbial genetics and the flow of genetic information. It defines key terms like genetics, genes, genome, genotype, and phenotype.
2. It describes the structure of DNA and how it carries genetic information as a double-stranded molecule made up of nucleotides. DNA replication is semi-conservative and involves unwinding the strands, creating an RNA primer, and synthesizing new strands in the 5' to 3' direction.
3. The process of transcription is described, where RNA polymerase reads the genetic code from DNA and synthesizes mRNA, which is then translated to produce proteins. Both prokaryotes and eukaryotes undergo transcription but differ in initiation, processing, and coupling with
DNA replication involves the formation of a molecule complementary in shape and this, in
turn, would serve as a template to make a replica of the original molecule.
• Chromosomal DNA replication occurs only during the S phase of the cell cycle.
• In eukaryotes, every base pair in each chromosome be replicated once and only once each
time a cell divides.
• The combination of all the proteins that function at the replication fork is referred to as
the replisome.
The document summarizes DNA replication. It describes that DNA replication produces two identical copies of DNA from one original molecule through a semi-conservative process. This involves unwinding of DNA at origins of replication by helicase to form replication forks that grow bidirectionally. DNA polymerase then synthesizes new strands using the original strands as templates. Replication occurs through initiation, elongation, and termination steps mediated by various proteins at the replication fork. The Meselson-Stahl experiment provided evidence that DNA replication is semi-conservative through density gradient centrifugation of parental and progeny DNA.
DNA replication is the process whereby a cell makes an identical copy of its DNA before cell division. It ensures faithful inheritance of genetic material during cell division. DNA replication is semi-conservative and bidirectional, occurring simultaneously on both strands of the DNA double helix to produce two identical copies. It involves unwinding of the DNA double helix by helicase, synthesis of new strands by DNA polymerases along leading and lagging strands using existing strands as templates, and ligation of fragments by DNA ligase. DNA replication is tightly regulated during the S phase of the cell cycle and is essential for accurate transmission of genetic information from parent to daughter cells.
DNA recombination mechanisms are involved in DNA repair, replication, gene expression and chromosome segregation. Recombination involves the breakage and joining of DNA strands. There are three main classes of recombination: homologous recombination between similar DNA sequences, site-specific recombination occurring at particular DNA sequences, and DNA transposition where segments of DNA move to new locations. Recombination is mediated by enzymes and involves steps like strand exchange, branch migration and resolution of Holliday junction structures to produce recombinant DNA products.
Prokaryotic DNA replication : These slides contains basics of the prokaryotic DNA replication for S.Y.B.Sc and T.Y.B.Sc students of Microbiology and biotechnology
It covers topics like Enzymes used in replication, Semiconservative replication, Meselson and Stahl experiment, Termination of replication, modes of replication: theta and rolling circle, basic rules of replication
DNA replication is the process by which DNA copies itself for cell division. It is semi-conservative, starting at the origin and proceeding bidirectionally. The leading strand is synthesized continuously while the lagging strand is synthesized discontinuously in fragments called Okazaki fragments. RNA primers are required for initiation. DNA polymerase adds nucleotides to the 3' end of the growing strand based on complementary base pairing. Topoisomerases relieve torsional strain from unwinding. DNA ligase seals fragments on the lagging strand. Replication terminates when forks meet on the opposite side of circular DNA in prokaryotes.
Recombinant DNA technology involves combining DNA from different sources and introducing it into a host cell. This allows for precise genetic analysis and practical applications. Key developments included elucidating DNA structure, cracking the genetic code, and describing transcription and translation. Gene cloning was developed in the 1970s, enabling previously impossible experiments. It involves isolating DNA, cutting it with restriction enzymes, ligating it into a vector, transforming host cells to amplify the recombinant DNA. The polymerase chain reaction (PCR) allows amplifying specific DNA regions without living cells by repeated heating and cooling in a test tube. It has revolutionized research fields like genetics and molecular biology.
DNA was discovered in 1868 and carries genetic traits. It is a double-stranded molecule composed of nucleotides that code for inherited characteristics. DNA replication is the process where DNA copies itself during cell division. It occurs in three main steps - initiation, elongation, and proofreading. DNA recombination and mutation can result in changes to the DNA sequence, altering traits or introducing variation. Recombinant DNA techniques cut and join DNA from different sources to produce modified sequences.
The document discusses three models of DNA replication:
1) Asymmetric replication - the leading and lagging strands are replicated differently due to the 5' to 3' directionality of DNA polymerase. The leading strand replicates continuously while the lagging strand replicates discontinuously in short Okazaki fragments.
2) D-loop model - replication in mitochondria where one strand is displaced to form a D-loop and replicates first before the other strand.
3) Rolling circle model - used by plasmids and viruses where one strand is nicked and displaced to be used as a template, forming multiple copies linked together in a concatemer.
Recombination is a fundamental genetic process that occursghorbian20
1. Homologous recombination and site-specific recombination are essential DNA repair and genetic diversity mechanisms. Homologous recombination occurs between similar DNA sequences during meiosis and mitosis, while site-specific recombination involves cleavage and rejoining between specific DNA sites.
2. Double-strand breaks initiate homologous recombination through end resection, strand invasion, and formation of Holliday junctions. These junctions are resolved to form crossover or non-crossover products.
3. Specialized systems, like lambda integration and yeast mating type switching, utilize site-specific recombinases that catalyze recombination between specific DNA sequences.
Able to define replication in the context of the central dogma.
Able to understand the basic mechanism of DNA replication and know the various enzymes that play a role in this process.
Able to know proofreading and repair mechanisms of DNA replications
This document discusses nucleotides, nucleic acids, and heredity. It begins by explaining that cells contain thousands of proteins and chromosomes carry hereditary information in genes made of DNA and histone proteins. The document then discusses that DNA carries genetic information in genes and each gene controls one protein. It describes the basic components and structures of nucleic acids DNA and RNA, including nucleotides, bases, nucleosides, and primary and secondary structures. It explains how DNA replicates and is amplified through PCR. The roles of different RNA types and protein synthesis are covered. The document concludes by discussing DNA repair through the base excision repair pathway.
DNA replication involves separating the two strands of the DNA double helix to serve as templates for producing two new DNA molecules. Each new molecule contains one old strand and one newly synthesized strand. This process of semiconservative replication ensures that each cell receives a complete copy of the genome upon division. DNA polymerases are the key enzymes that catalyze DNA replication by adding nucleotides to the 3' end of a growing DNA strand in a 5' to 3' direction. Replication occurs bidirectionally from an origin of replication.
The nucleotide structure ,consists of
the nitrogenous base ,attached to the 1’ carbon of deoxyribose
,
the phosphate group attached to the 5’ carbon of deoxyribose
,
a free hydroxyl group (-OH) ,at the 3’ carbon of deoxyribose,1. DNA HELICASES,
to separate the strand,
2. GYRASE (Topoisomerases),
unwind the supercoil,
3. Single strand binding protein (SSBP)
, activity of helicase,
keep two strand separate,
protect DNA from nuclease degradation,
release after replication,
DNA replication is a highly regulated process that exactly duplicates the genome during cell division. It involves unwinding of the DNA double helix at the origin of replication by helicase. Each single-stranded template is then used to synthesize a new complementary strand in the 5'-to-3' direction by DNA polymerase. The leading strand is replicated continuously while the lagging strand is replicated discontinuously in short segments called Okazaki fragments that are later joined by ligase. Several proteins and enzymes work together in a coordinated manner to ensure the genome is accurately duplicated and inherited by daughter cells.
DNA replication is a highly regulated process that occurs semiconservatively before cell division. It involves unwinding of the DNA double helix by helicases, followed by synthesis of new strands complementary to each parental strand. This is carried out by DNA polymerases that add nucleotides according to base pairing rules. In eukaryotes, the lagging strand is synthesized discontinuously in fragments called Okazaki fragments which are later joined by DNA ligase. DNA replication ensures faithful transmission of genetic material to daughter cells.
Similar to Recombination : types, models........... (20)
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
ESPP presentation to EU Waste Water Network, 4th June 2024 “EU policies driving nutrient removal and recycling
and the revised UWWTD (Urban Waste Water Treatment Directive)”
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
Unlocking the mysteries of reproduction: Exploring fecundity and gonadosomati...AbdullaAlAsif1
The pygmy halfbeak Dermogenys colletei, is known for its viviparous nature, this presents an intriguing case of relatively low fecundity, raising questions about potential compensatory reproductive strategies employed by this species. Our study delves into the examination of fecundity and the Gonadosomatic Index (GSI) in the Pygmy Halfbeak, D. colletei (Meisner, 2001), an intriguing viviparous fish indigenous to Sarawak, Borneo. We hypothesize that the Pygmy halfbeak, D. colletei, may exhibit unique reproductive adaptations to offset its low fecundity, thus enhancing its survival and fitness. To address this, we conducted a comprehensive study utilizing 28 mature female specimens of D. colletei, carefully measuring fecundity and GSI to shed light on the reproductive adaptations of this species. Our findings reveal that D. colletei indeed exhibits low fecundity, with a mean of 16.76 ± 2.01, and a mean GSI of 12.83 ± 1.27, providing crucial insights into the reproductive mechanisms at play in this species. These results underscore the existence of unique reproductive strategies in D. colletei, enabling its adaptation and persistence in Borneo's diverse aquatic ecosystems, and call for further ecological research to elucidate these mechanisms. This study lends to a better understanding of viviparous fish in Borneo and contributes to the broader field of aquatic ecology, enhancing our knowledge of species adaptations to unique ecological challenges.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
hematic appreciation test is a psychological assessment tool used to measure an individual's appreciation and understanding of specific themes or topics. This test helps to evaluate an individual's ability to connect different ideas and concepts within a given theme, as well as their overall comprehension and interpretation skills. The results of the test can provide valuable insights into an individual's cognitive abilities, creativity, and critical thinking skills
Remote Sensing and Computational, Evolutionary, Supercomputing, and Intellige...University of Maribor
Slides from talk:
Aleš Zamuda: Remote Sensing and Computational, Evolutionary, Supercomputing, and Intelligent Systems.
11th International Conference on Electrical, Electronics and Computer Engineering (IcETRAN), Niš, 3-6 June 2024
Inter-Society Networking Panel GRSS/MTT-S/CIS Panel Session: Promoting Connection and Cooperation
https://www.etran.rs/2024/en/home-english/
Or: Beyond linear.
Abstract: Equivariant neural networks are neural networks that incorporate symmetries. The nonlinear activation functions in these networks result in interesting nonlinear equivariant maps between simple representations, and motivate the key player of this talk: piecewise linear representation theory.
Disclaimer: No one is perfect, so please mind that there might be mistakes and typos.
dtubbenhauer@gmail.com
Corrected slides: dtubbenhauer.com/talks.html
ESA/ACT Science Coffee: Diego Blas - Gravitational wave detection with orbita...Advanced-Concepts-Team
Presentation in the Science Coffee of the Advanced Concepts Team of the European Space Agency on the 07.06.2024.
Speaker: Diego Blas (IFAE/ICREA)
Title: Gravitational wave detection with orbital motion of Moon and artificial
Abstract:
In this talk I will describe some recent ideas to find gravitational waves from supermassive black holes or of primordial origin by studying their secular effect on the orbital motion of the Moon or satellites that are laser ranged.
1. RECOMBINATION
Submitted to: Submitted By:
I.K Nishitha Aleena Stanley
Assistant Prof: 1st MSc Botany
Dept of Botany St.Teresa’s College
St.Teresa’s College
1
2. RECOMBINATION
● Recombination is the rearrangement of DNA
molecule or formation of new combination of
genes.
● Recombination by crossing over is the process
most molecular biologists often associate with the
term recombination.
● But crossing over is not only the mechanism for
recombination.
2
3. Three Mechanisms by which recombination can take place;
1. Homologous Recombination
2. Non-Homologous Recombination
3. Site specific recombination
4. Transposition
These are important mechanisms for DNA
rearrangement(Recombination)
3
4. HOMOLOGOUS RECOMBINATION (Generalized recombination)
It is the process whereby DNA segments that are similar or identical to each other
break and rejoin to form a new combination.
Note: Homologous Recombination- occurs between DNA molecules of very similar or identical
sequence.
4
5. Two types of crossing over may occur between replicated chromosomes in a
diploid species:-
1. Sister Chromatid Exchange (SCE)
It Occurs between sister chromatids- genetically identical chromatids- doesn’t
produce new combination of alleles.
5
6. 2.Homologous Recombination
It occurs when homologous chromosomes cross over- produce new combination
of alleles; result in genetic recombination
6
7. ● It is most widely used by cells to accurately repair harmful
breaks that occur on both strands of DNA, known as
double strand breaks.
● These new combinations of DNA represent genetic
variation in offspring, which in turn enables populations to
adapt during the course of evolution.
7
8. Models Explaining Homologous Recombination
1. Holliday Model
2. Meselson- Radding Model
3. Double- strand Break Model
8
9. 1.HOLLIDAY MODEL
● Robin Holliday proposed a model in
1964 to explain the molecular steps
that occur during homologous
recombination.
● This model describes a molecular
mechanism of the recombination
process.
9
10. Steps in Homologous Recombination
Alignment of
two
homologous
DNA
molecules.
1
Introduction
of breaks in
the DNA.
2
Strand
invasion.
3
Formation of
the Holliday
junction.
4
Resolution of
the Holliday
junction.
5
10
11. Holliday Model-Steps
1. Two homologous chromatids are
aligned with each other.
2. A break or nick occur at identical sites
in one strand of each of the two
homologous chromatids.
3. The strands then invade the opposite
helices and base-pair with the
complementary strands.
4. This event followed by the covalent
linkage to create a Holliday junction.
11
12. 5. When the two strands have crossed over and DNA ligase sealed the new
intermolecular phosphodiester bonds, a Holliday Junction is created- also
Known as chiasma or chi structure.
Holliday Junction
12
13. 6. A Holliday Junction can move along the DNA by the repeated melting and formation
of base pairs- BRANCH MIGRATION.
13
14. 7. Because the DNA sequence in the homologous chromosomes are similar but
may not be identical, the swapping of the DNA strands during branch migration
may produce a heteroduplex.
14
15. 8. The final step in the recombination process is called
resolution because they involve the breakage and
rejoining of two DNA strands to create two separate
chromosomes. It is the step to regenerate DNA molecule
and therefore finish genetic exchange.
Two ways a resolution can happen, In this 2DNA’s are recombined
and it can be found in single plain after rotating.
( All the DNA Strands are on the same plane). Here 2 DNA strands
are crossing each other. So to separate the crossing - vertically
and horizontally.
15
16. Here the 2 DNA Strands are recombined(each
made of 2 nucleotide seq). So each strands
are crossover strands.
Here in Both of the 2 DNA strand one
strand is conserved. And one strand is
recombined and these products are called
non crossover products.
16
17. 2.The Meselson- Radding Model
● Proposed by Mathew Meselson and Charles Radding in
1975.
● Hypothesized that a single nick in one DNA strand initiates
recombination.
17
18. ● This model suggests, Single-
strand nick occurs in one of the
double helices, one of the free
end invades the homologous
double helix( unbroken),
displacing one of its strands
forming a D-loop
(Displacement loop)
D loop 18
19. ● Eventually second nick occurs at the
D-loop, creating the Holliday
structure.
19
20. ● The Final steps( branch migration
and resolution) is as same as in
Holliday model.
20
21. 3. The Double strand Break (DSB) Model
● Proposed by Jack Szostak, Terry Orr-Weaver, Rodney Rothstein and
Franklin Stahl.
● Suggests that a double- strand break initiates the recombination process.
● Recent evidence suggests that double- strand breaks commonly promote
homologous recombination during meiosis and during DNA repair.
21
22. ● Formation of a double strand break in one of
the chromosome .
● A small region near the break is degraded,
which generates a single stranded (with 3’0H)
segment that can invade the intact double
helix.
● The strand displaced by the invading segment
forms a structure called displacement loop.
22
23. ● After the D-loop is formed, two
regions have a gap in the DNA.
● DNA synthesis occurs in the
relatively short gaps where a
DNA strand is missing.
● This DNA synthesis is called
DNA gap repair synthesis.
● Once this completed, two
Holliday junctions are formed.
23
24. Depending on the way these are resolved, the end result is non recombinant
or recombinant chromosomes containing short duplex.
24
25. DSB Repair Model
A DNA-cleaving enzyme
sequentially degrades the
broken DNA molecule to
generate regions of
single-stranded DNA
(ssDNA).
Creation of ssDNA tails
which terminate with
3' ends.
The invading strand
base-pairs with its
complementary strand
in the other DNA
molecule.
Introduction of a DSB
in one of two
homologous duplex
DNA molecules.
25
26. The invading strands
with 30 termini serve as
primers for new DNA
synthesis.
Elongation from these
DNA ends using the
complementary strand in
the homologous duplex
as a template.
Gene conversion event.
The two Holliday junctions
found in the recombination
intermediates generated by
this model move by branch
migration.
Resolution.
26
28. RecA Protein
● RecA Protein is about 350 amino acids residues. Its sequence is highly conserved
among eubacterial species.
RecA protein involved in homologous recombination and bypass mutagenic DNA
lesions by SOS response.
1) ATP-driven homologous pairing and strand exchange of DNA molecules necessary for
DNA recombination repair.
2) ATP-dependent uptake of single stranded DNA by duplex DNA
3) ATP-dependent hybridization of homologous single-stranded DNAs.
28
29. The RecBCD Helicase/Nuclease
• Processes broken DNA molecules to generate these regions of ssDNA.
• Helps load the RecA strand-exchange protein onto these ssDNA ends.
• Multiple enzymatic activities of RecBCD provide a means for cells to
“determine” whether to recombine with or destroy DNA molecules that
enter a cell.
• Has both DNA helicase and nuclease activities.
• The complex binds to DNA molecules at the site of a DSB and tracks along
DNA using the energy of ATP hydrolysis.
• The DNA is unwound, with or without the accompanying nucleolytic
destruction of one or both of the DNA strands.
29
30. • composed of three subunits (the products of the recB, recC, and recD genes)
30
31. ● The Rec B protein contains 1180 residues and is modular .
● The N terminal contains the helicase activity and has seven characteristic SF1 motifs 1,1a, 2, 3,
4,5 and 6
● The C terminal domain contains nucleases motifs. “Nuc” marks the position of nuclease activity
contains aspartate and lysine residues.
● The Rec C protein has 1122 aa residues and contains chi recognition site.
● The Rec D protein with 608 aa residues has SF1 seven helicase motifs. (1, 1a, 2, 3, 4, 5
and6 )
Rec B
Rec C
Rec D
31
32. RecBCD-catalyzed DNA end-processing reaction.
● DNA ends resulting from a double- strand break is
processed by a multi functional enzyme complex
called RecBCD.
● RecBCD is a sequence- regulated bipolar helicase
nuclease that splits the duplex into its component
strands and digests them until it encounters Chi site.
● Chi site - Recombination Hotspot
● (5’-GCTGGTGG-3’)
32
33. 1) The RecBCD binds tightly to a blunt DNA end of
a linear DNA duplex.
2) RecBCd couples the hydrolysis of ATP to DNA
translocation and unwinding. The ssDNA
products are cleaved asymmetrically, with the
degradation on the 3’- terminated ssDNA tail
being much more vigorous than the degradation
of the complementary tail.
3) The enzyme continues the translocation until it
pauses at a correctly oriented Chi sequence.
After Chi sequence recognition RecBCD
facilitates the loading of the RecA protein onto
the 3’ ssDNA tail.
4) The enzyme continues to translocate, but the
nuclease polarity is switched; the degradation of
3’ ssDNA tail is attenuated, whereas the
hydrolysis of the 5’ ssDNA tail is upregulated. 33
34. 5) RecBCD repeatedly deposits RecA
promoters, which act as nucleation points for
filament growth primarily in the 5’-3’ direction.
6) RecBCD enzyme dissociates from the DNA .
The product of the enzyme is recombinogenic
nucleoprotein complex of the RecA protein
bound to the 3’ ssDNA tail with Chi at its
terminus.
The product invade homologous duplex DNA to
promote the recombinational repair of a DSB or
to restart DNA replication.
34
35. Non Homologous Recombination
● Non-homologous recombination
refers to a DNA rearrangement
that leads to covalent joining of
non-homologous linear DNA
segments.
● Occurs in most gram positive
bacteria.
● E.g Kluyveromyces lactis
35
36. ROLE OF Ku PROTEIN
● Ku is abundant, highly conserved DNA binding protein found in both
prokaryotes and eukaryotes that play essential roles in the maintenance of
genome integrity.
● In eukaryotes, Ku is a heterodimer comprised of two subunits, Ku70 and Ku80
that is best characterized for its central role as the initial DNA end binding
factor in the “classical” C-NHEJ pathway.
● Ku binds dsDNA ends with high affinity in a sequence-independent manner
through a central ring formed by the intertwined strands of the Ku70 and Ku80
subunits.
36
37. Canonical non-homologous end joining pathway(C-NHEJ)
C-NHEJ depends on Ku heterodimer and DNA- PK
catalytic subunit( DNA-PKcs), which together form the
DNA -PK holoenzyme.
Unlike MRN, which can bind internally, Ku requires a
free DNA end for binding and cannot associate with
most blocked ends.
Several nucleases including (TDP1/2) and Artemis can
remove hairpins, damaged bases or proteins -DNA
adducts.
The DNA ends are processed by additional enzymes
and rejoined by the LIG4/XRCC4/XLF complex.
37