1 DNA, the genetic materialKatalin Kiss

2 The role of DNA was unknown Friedrich Miescher : DNA („nuclein”) in the nucleus of white blood cells The role of DNA was unknown Theory: proteins code for genetic information First half of 1900’: Experiments proving the „genetic role” of DNA Griffith and Avery and his colleauges : „bacterium transformation”experiments Hershey-Chase 1952.: „bacteriophage infection experiment”

3 Bacterium transformation experimentsFrederick Griffith: Introduction of term „transformation” Scientific messages: The transforming material is heat resistant Proteins do not code for the genetic information Oswald Avery, Colin MacLeod, and Maclyn McCarty: DNA causes transformation DNA is the genetic material

4 Bacteriophage experiment Alfred Day Hershey és Martha Chase: DNA is responsible for the viral infection and the reprograming of host cells

5 Replication Katalin Kiss

6 replication= DNA synthesis = making 2 identical copies of DNA2 double stranded DNA molecules are made from 1 double stranded DNA molecule point of time in life of cell: before cell division (in eukaryotes in S phase) significance: to make 2 identical copies of each DNA molecule for the daughter cells basis of inheritance of genetic information from parents to offsprings

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8 Structure of DNA Monomers: nucleotides (2’ deoxyribonucleoside-monophosphates in the chain and deoxyribonucleoside-triphosphate at 5’ end) 3’-5’ phosphodiester bonds 5’ and 3’ ends Double stranded Antiparallel orientation Complementary base pairing (A-T, G-C); H-bonds

9 Process of replicationInitiation: ori is recognized by proteins 2 strands are separated by cleaving the H bonds primer binding Elongation: in replication bubble complementary nucleotide binds to template strand with H bonds DNA polymerase forms 3’-5’ phosphodiester bond Termination separation of 2 dsDNA molecules from each other

10 Replication bubble ori Replication fork

11 Replication fork

12 motifolio.com

13 General features of replicationMultienzyme complex= replisome does replication starts at Origin =ori site in prokaryotes: 1; in eukaryotes: several/ 1 DNA Bidirectional (in 2 directions from ori) Semiconservative (1 parental and 1 daughter strand in new DNA) Semidiscontinuous (2 types of new strands: continuously made leading strand; discontinuously made lagging strand) DNA polymerase: forms 3’-5’phosphodiester bonds Substrates: deoxyribonucleoside-triphosphates Template dependent Primer dependent Energy-dependent (high energy bonds in nucleotides serve energy) Direction: Synthesis of the new strand: from 5’ to 3’ end DNA polymerase movement on template: from 3’ to 5’ end

14 PNAS Vol. 104, pp , 2007 PNAS Vol. 71, No. 1, pp , January 1974