Life Histories and Natural Selection, 242. For their discovery of telomerase and its action, Elizabeth Blackburn, Carol W. Greider, and Jack W. Szostak ((Figure)) received the Nobel Prize for Medicine and Physiology in 2009. DNA Repair: 70 DNA Repair DNA repair mechanisms can be: specific – targeting a particular type of DNA damage photorepair of thymine dimers non-specific – able to repair many different kinds of DNA damage excision repair to correct damaged or mismatched nitrogenous bases DNA Repair: DNA Repair Excision repair: 1. Scientists have studied the prokaryotic mechanism of DNA replication and outlined it in detail. Synthesis of Biological Macromolecules, 20. Mcm10 Required for initiation and elongation stages of DNA replication. It’s major role is to pass the genetic information from parents to offspring without any error. Synthesis Phase (S phase): Synthesis Phase (S phase) S phase in i nterphase of the cell cycle . contact the author of the presentation. Eukaryotic Transcription Gene Regulation, 83. (Note: Unlike as in eukaryotic mRNA, the prokaryotic mRNA does not receive a 5’ cap) 5.) DNA polymerase activity was discovered by Kornberg in 1956; this activity was due to DNA polymerase I. E. coli has four more enzymes, DNA polymerase II, III (Table. This is the process by which the genome of prokaryotic cells duplicates so that it can be transformed into a daughter cell. Before replication can start, the DNA has to be made available as a template. Slide18: Prokaryotic DNA Replication Eukaryotic DNA replication Occurs inside the cytoplasm Occurs inside the nucleus Only one origin of replication per molecule of DNA Have many origins of replication in each chromosome Origin of replication is about 100-200 or more nucleotides in length Each origin of replication is formed of about 150 nucleotides Replication occurs at one point in … Cdc45 Required for initiation and elongation steps of DNA replication. Dna replication eukaryotes 1. ELONGATION: 2. Associates with pre-replicative complex around the time of initiation and moves with replication forks during elongation step. Flash The RNA primers are replaced with DNA nucleotides; the DNA Okazaki fragments are linked into one continuous strand by DNA ligase. Evolution and the Origin of Species, 102. The Okazaki fragments in the lagging strand are joined after the replacement of the RNA primers with DNA. g : Mitochondrial DNA polymerase d : Is responsible for the replication on the leading strand of DNA. Determining Evolutionary Relationships, 103. DNA ligase: joins 3’ end of each fragment to 5’ end of another. Slide60: Okazaki Fragments 2. HTTPS (Hypertext Transfer Protocol Secure) is a protocol used by Web servers to transfer and display Web content securely. Replication Protein A  (RPA) Heterotrimeric single-stranded binding protein. The ends of the linear chromosomes are maintained by. It also possesses proof reading activity. Proliferating cell nuclear antigen (PCNA) Trimeric protein with ring shaped structure, encloses DNA preventing dissociation of DNA polymerase. The DNA at the ends of the chromosome thus remains unpaired, and over time these ends, called telomeres, may get progressively shorter as cells continue to divide. Different phases and their functions :: Different phases and their function s : DNA Replication: Basic Concept: DNA Replication: Basic Concept After separation, each parental strand becomes a template Complementary pairing Each “daughter” molecule has one parental strand and one new strand. Environmental Limits to Population Growth, 246. DNA replication is a biological process by which the two genetically identical replicas of DNA are synthesized from a single, original DNA molecule. INITIATION Pre-replicative Complex: Pre-replicative Complex RNA primer is needed during replication: 57 RNA primer is needed during replication RNA primer is a short amount of RNA, complementary to the DNA strand being replicated. The essential steps of replication are the same as in prokaryotes. characteristic semi-discontinuous replication Slide18: Prokaryotic DNA Replication Eukaryotic DNA replication Occurs inside the cytoplasm Occurs inside the nucleus Only one origin of replication per molecule of DNA Have many origins of replication in each chromosome Origin of replication is about 100-200 or more nucleotides in length Each origin of replication is formed of about 150 nucleotides Replication occurs at one point in each chromosome Replication occurs at several points simultaneously in each chromosome Only one replication fork is formed Multiple replication forks are formed simultaneously in each chromosome Only have one origin of replication Has multiple origins of replication Initiation is carried out by protein DnaA and DnaB Initiation is carried out by the Origin Recognition Complex Topoisomerase is needed Topoisomerase is needed Replication is very rapid Replication is very slow Enzymes of replication : 19 Enzymes of replication Helicase DNA ploymerase DNA ligase Primase Topoisomerase Key Enzymes in DNA replication: 20 Key Enzymes in DNA replication Mammalian DNA Polymerases: Mammalian DNA Polymerases a : Is responsible for the synthesis of RNA primer for the leading and Lagging strands of DNA. The Animal Body: Basic Form and Function, XXXIV. Other Acellular Entities: Prions and Viroids, 111. Loads DNA polymerase ε onto pre-replication complexes at origins. : What is eukaryotic DNA replication ??? DnaA– it recognizes oriCsequenc… As replication progresses and the replisome moves forward, DNA polymerase III arrives at the RNA primer and begins replicating the DNA, adding onto the 3'OH of the primer DNA … Ligase activity also needed for DNA repair and recombination. Thus, the ends of the chromosomes are replicated. With the advent of modern medicine, preventative health care, and healthier lifestyles, the human life span has increased, and there is an increasing demand for people to look younger and have a better quality of life as they grow older. : It is the multiplication of a “Double helical DNA” into the multiple DNAs undergoing various biological and physiological phenomenon. If not remedied, the DNA would become shorter and shorter Telomerase resolves the terminal primer problem Telomerase: Telomerase Telomerase = enzyme made up of both protein and RNA RNA component is base sequence complementary to telomere repeat unit Catalyzes synthesis of new DNA using RNA as template Slide39: End-Replication Problem 5 3 5 3 5 3 5 3 + + 5 3 5 3 Process Okazaki Fragments Slide40: Telomere Structure Telomeres composed of short (6-10 bp ) repeats G-rich in one strand, C-rich in other 5 3 G-rich C-rich Slide42: Telomerase Germ-line cells possess telomerase activity Most human somatic cells lack telomerase activity Cultured immortal cell lines have been shown to have telomerase activity Possible cancer therapy may be to control telomerase activity in cancer cells Slide43: The eukaryotic replication machinery is generally similar to that of E. coli Slide44: 44 DNA ploymerase and DNA ligase: 45 DNA ploymerase : joins individual nucleotides together in complementary strands. Replication in eukaryotes ... Eukaryotic DNA Replication: ... 4 DNA polymerase complexes (2 per replication fork) at oriC ... – A free PowerPoint PPT presentation (displayed as a Flash slide show) on PowerShow.com - id: 5e689-ZDc1Z eukaryotic replication has been gained from studying yeast and SV-40 DNA replication. If the action of telomerase in these cells can be inhibited by drugs during cancer therapy, then the cancerous cells could potentially be stopped from further division. Historical Basis of Modern Understanding, 81. Histones must be removed and then replaced during the replication process, which helps to account for the lower replication rate in eukaryotes. Atoms, Isotopes, Ions, and Molecules: The Building Blocks, 9. Transport of Gases in Human Bodily Fluids, 213. Watson and Crick showed: the two strands of the parental molecule separate, and each functions as a template for synthesis of a new complementary strand. DNA 5’-GCGTATG-3’ 3’-CGCATAC-5’ Slide75: Protein Function in Eukaryotic DNA replication AND1 Loads DNA Polymerase α onto chromatin together with CMG complex on the lagging strand. Key substrate of CDK, phosphorylation promotes interaction with Dpb11. (credit: US Embassy Sweden), Jaskelioff et al., “Telomerase reactivation reverses tissue degeneration in aged telomerase-deficient mice,”, Creative Commons Attribution 4.0 International License, Discuss the similarities and differences between DNA replication in eukaryotes and prokaryotes, State the role of telomerase in DNA replication. The chromatin (the complex between DNA and proteins) may undergo some chemical modifications, so that the DNA may be able to slide off the proteins or be accessible to the enzymes of the DNA replication … ELONGATION The leading strand and lagging strand: 63 The leading strand and lagging strand Leading strand: in the 5’→3’direction, synthesized continuously. Dynamic Each body cell gets a complete set of identical DNA. : Role of replisome !!! Thus, telomere reactivation may have potential for treating age-related diseases in humans. Fen1 5’ flap endonuclease involved in processing Okazaki fragments. The telomerase enzyme contains a catalytic part and a built-in RNA template. b : Repair function and similar to DNA polymerase I found in prokaryotes. DNA replication is the most fundamental action. : We can see these bubbles! Replication is the process in which a single strand of nucleotides acts as a template for the formation of a complementary strand. Parental DNA DNA Template New DNA Conservation of heredity (high fidelity of replication): 16 Conservation of heredity ( high fidelity of replication) Following replication, the daughter molecules each have a new strand and an old strand. Behavioral Biology: Proximate and Ultimate Causes of Behavior, XLVII. While the leading strand is continuously synthesized by the enzyme pol δ, the lagging strand is synthesized by pol ε. Required for initiation of replication. © 2014 authorSTREAM. The whole process takes place with the help of enzymes where DNA-dependent DNA polymerase being the chief enzyme. Required for initiation of replication. So, what happens in between parent DNA being converted into the new DNAs ? Origin Recognition Complex  (ORC) Heterohexameric complex composed of Orc1 - Orc6 proteins. Prokaryotic DNA Replication. View Cell Division-b.ppt from BIO MISC at University of South Florida. E. coli DNA is contained within a single, circular chromosome. ARS (autonomously replicating sequence) in case of yeast is origin for replication. It attaches to the end of the chromosome, and DNA nucleotides complementary to the RNA template are added on the 3′ end of the DNA strand. A sliding clamp protein known as PCNA (proliferating cell nuclear antigen) holds the DNA pol in place so that it does not slide off the DNA. Acts as a sliding clamp for polymerases δ and ε, thereby improving processivity of replicative polymerases. Replication in eukaryotes starts at multiple origins of replication. Superphylum Lophotrochozoa: Molluscs and Annelids, 146. Key Terms. Eukaryotic DNA is bound to basic proteins known as histones to form structures called nucleosomes. Replication forks are formed at each replication origin as the DNA unwinds. DNA polymerase and DNA ligase replace and bond the new nucleotides together. DNA Polymerase δ (Pol δ) Required to complete synthesis of Okazaki fragments on the lagging strand that have been started by DNA polymerase α. DNA Polymerase ε (Pol ε) The leading strand polymerase. Slide78: RNase H Ribonuclease which digests RNA hybridized to DNA. They are known as pol α, pol β, pol γ, pol δ, and pol ε. Homolog in metazoans is known as AND-1. RNA Polymerase is the enzyme that produces the mRNA molecule (just like DNA polymerase produced a new DNA molecule during DNA replication). 2. For most cell types these sites lack a well-defined sequence signature, so it is not understood how they are selected. A single origin of replication results in the formation of two replication forks. Copy, EUKARYOTIC DNA REPLICATION: EUKARYOTIC DNA REPLICATION -Ujwal L abh Objectives:: Objectives: Outline the mechanisms of eukaryotic DNA replication Describe the cellular mechanisms that help avoid error generation during DNA synthesis Describe the possible pathways of DNA repair Relate chromatin density and the cell cycle to DNA replication What is eukaryotic DNA replication ??? Cyclin-dependent kinase  (CDK) Cyclin-dependent protein kinase required for initiation of replication and for other subsequent steps. You do not have the permission to view this presentation. DNA replication in prokaryotes has been extensively studied, so we will learn the basic process of prokaryotic DNA replication, then focus on the differences between prokaryotes and eukaryotes. Eukaryotic DNA is bound to basic proteins known as histones to form structures called nucleosomes. All rights reserved. Cells that undergo cell division continue to have their telomeres shortened because most somatic cells do not make telomerase. Telomerase has an inbuilt RNA template that extends the 3′ end, so primer is synthesized and extended. These are resolved with the action of topoisomerases. Replication is semiconservative Direction of DNA Replication: 10 Direction of DNA Replication 5 ’ →3 ’ MODES OF REPLICATION : MODES OF REPLICATION characteristic Semiconservative Replication: 13 Semiconservative replication would produce two copies that each contained one of the original strands and one new strand. Customize Embed, Thumbnail: Eukaryotic Translational and Post-translational Gene Regulation, XVIII. By the end of this section, you will be able to do the following: Eukaryotic genomes are much more complex and larger in size than prokaryotic genomes. Viral Evolution, Morphology, and Classification, 107. The number of DNA polymerases in eukaryotes is much more than in prokaryotes: 14 are known, of which five are known to have major roles during replication and have been well studied. A daughter DNA double helix has the same sequence of bases as the parent DNA double helix had originally. Telomerase, an enzyme with an inbuilt RNA template, extends the ends by copying the RNA template and extending one strand of the chromosome. In conservative replication, the parental DNA remains together, and the newly formed daughter strands are together. By : Sheetal paradhi MSC botany.. 2. These subunits assemble every time a gene is transcribed, and they disassemble once transcription is complete. The Evolutionary History of the Animal Kingdom, 144. Telomeres comprise repetitive sequences that code for no particular gene. Replication Fork: Replication Fork 3. TERMINATION DNA Repair: 69 DNA Repair Mistakes during DNA replication can lead to changes in the DNA sequence and DNA damage. DNA Replication in Eukaryotes Slide49: Copyright ©The McGraw-Hill Companies, Inc. Initiation Complex: Initiation Complex We can see these bubbles! Copy, Automatically changes to Flash or non-Flash embed, WordPress Embed Slide22: Problems that must be overcome for DNA polymerase to copy DNA DNA polymerases can’t melt duplex DNA Must be separated for copying DNA polymerases can only elongate a preexisting DNA or RNA strand (the primer) Strands in the DNA duplex are opposite in chemical polarity All DNA polymerases catalyze nucleotide addition at 3  -hydroxyl end Strands can grow only in the 5  to 3  direction DNA Helicase: DNA Helicase Hexameric ring Separate DNA strands Use 2ATP hydrolysis for Energy Primase: Primase Activated by helicase Synthesizes short RNA primer Uses DNA as template Sliding clamp: Sliding clamp Keeps DNA polymerases attached to DNA strand Assisted by clamp loader through ATP hydrolysis Will disassociate if DNA pol reaches DS DNA Single stranded binding proteins: Single stranded binding proteins Bind tightly and cooperatively to SS DNA Do not cover bases Remain available for templating Aid in stabilizing unwound DNA Prevent hairpin structures Slide27: Mammalian DNA polymerases Synthesize new DNA strand Requires primer DNA Pol a Associated with primase DNA Pol d Elongates Slide28: Topoisomerase Some proteins change topology of DNA Helicase can unwind the DNA duplex induce formation of supercoils Topoisomerases catalyze addition or removal of supercoils Slide29: Topoisomerase Type I topoisomerase relax DNA by nicking and closing one strand of duplex DNA Covalently attach to DNA phosphate Allow rotation Slide30: Topoisomerase Type II topoisomerase change DNA topology by breaking and rejoining double stranded DNA Slide31: Action of E coli Topoisomerase I Slide32: Type II topoisomerases ( gyrases ) change DNA topology by breaking and rejoining double-stranded DNA Slide33: Replicated circular DNA molecules are separated by type II topoisomerases Linear daughter chromatids also are separated by type II topoisomerases Slide34: Telomeres Further evidence of a relationship between telomere length and aging in humans Disorder called progerias (premature aging) Hutchinson-Gilford Syndrome (severe) – death in the teen years Werner Syndrome (less severe) – death usually in the 40s Slide35: Telomere Replication Regions of DNA at each end of a linear chromosome Required for replication and stability of that chromosome. 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Author of the presentation contact the author of the DNA is contained within dna replication in eukaryotes ppt authorstream strand!