BIOL 322 Entire Term Notes

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Biology (Biological Sciences)
Yan Boucher

Biology 322 Course Notes 12132013 14200 PM Topic One The Origins of LifeIntroduction to the Origin of LifeFormation of EarthStable hydrosphereprebiotic chemistrypreRNA worldRNA worldFirst DNAprotein lifeLast Universal Common Ancestor LUCAMillerUrey experiments showed that it was possible to synthesize basic molecules from the theorized environmental conditions of early earth It was also proven that the four nucleobases could be formed All the necessary components sugar nucelobases phosphates for the formation of RNA are present and it is possible to obtain RNA from early Earth Although it is possible it is not proven Clay may have played an important role in creating long strands of RNA This is because they allow the molecules to concentrate in the layers and link up similar to modern RNAo Clay acted as a catalyst facilitating the natural alignment of the RNA componentso Thus the ribonucelotide chain is capable of being formed Replicasecatalyzes that synthesis of the complimentary strando The additional activities that RNA can perform is more evidence of an RNA world Ribosomethe cellular machinery that catalyzes the growth of a peptide chaino It is made of RNA reads RNA and synthesizes proteino Provides evidence that the RNA world came first Modern RNA RolesTranslationo mRNAProduct of DNA transcription o tRNAInvolved in translation of the genetic code o rRNAServes as part of a ribosomal subunit DNA Replication o RNA primersReplication of the lagging DNA strand initiates with a DNA primero Telomerase RNANeeded at the ends of linear chromosomes Splicing and RNA Processing o snRNAInvolved in splicing o snoRNAPosttranscriptional processing of rRNA shows that RNA has many catalytic activities and enzyme function Ribozymes An RNA molecule capable of performing specific biochemical reactions similar to protein enzymes TypesSelfsplicing intronssome introns splice themselves by an autocatalytic process Ribonuclease Pcreates the 5 end of bacterial tRNAs Ribosomal RNAthe peptidyl transferase activity required for peptide bond formation during protein synthesis The Lipid Envelope Placing a replicase in a vesicle protects it from replicating everything around it In a membrane it only has access to itself Inner aqueous compartment of aphospholipid bilayer provides this One theory of the development of the lipid envelope is through geysers They release forming mini protocells When they are in a solution these molecules form an envelope spontaneously The ProtocellSelf replicatingable to divideMoleculesclaychainincorporated into a lipid bilayer lipids formed in geysers One theory Assisted reproduction via hotcold environments o At the warm side of the pond the RNA is warmed and denaturation occurs membranes grow and daughter cells separate On the cold side the single RNA strands act as a template on which new nucleotides formed base pairs So FarPreRNA worldo Prebiotic pool of random sequences o Prebiological compoundso Alternative genetic system such as RNADNA analogs or informational polymers using metal ions for catalytic activity Transition o RNA catalyzes its own replicationo Fidelity of replication improvedo Genome length reaches about 100 nucleotides RNA World o RNA as the only genetically encoded compoundo Evolution based on RNA replication via Watson Crick base pairingo Translation arises DNA replaces RNA o DNA copy made by RNA o Protein world evolvesOr o Protein world evolveso NTPsdNTPsDNA copy made by proteinsDNA WorldRNA world is the core to many thingstRNA catalytic RNAEvolution promotes better cellRNAProteinsDNADNA is more stable can encode more information leading to more stable genetic material Deoxyribonucleotide requires a reductase in order to be formed from a ribonucleotide DNA can selfreplicate but not efficiently A polymerase makes it more efficient Longer exposure of DNA to UV light lead to longer polymers Journey to the Modern Cell 1 Evolution Starts The first protocell is just a sac of water and RNA and requires an external stimulus such as cycles of heat and cole to reproduce2 RNA Catalysts Ribozymesfolded RNA molecules analogous to proteinbased enzymesarise and take on such jobs as speeding up reproduction and strengthening the protocells membrane The protocells then begin reproducing on their own3 Metabolism Begins Other ribozymes catalyze metabolismchains of chemical reactions that enable protocells to tap into nutrients from the environment4 Proteins Appear Complex systems of RNA catalysts begin to translate strings of RNA letters genes into chains of amino acids proteins Proteins later prove to be more efficient catalysts and able to carry out a variety of tasks5 Proteins Take Over Proteins take on a wide range of tasks within the cell Proteinbased catalysts or enzymes gradually replace most ribozymes 6 The Birth of DNA Other enzymes begin to make DNA Thanks to its superior stability DNA takes on the role of the primary genetic molecule RNAs main role is not to act as a bridge between DNA and protein7 Bacterial World
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