Rebecca Davenport BIOL 1406 BW1 10 27 16 Ch 16 blueprint 1 Molecular basis of inheritance a DNA Deoxyribonucleic acid a molecule that contains one s genetic makeup that is passed on to the next generation 1 A double stranded helix held together by hydrogen bonds a Antiparallel 3 to 5 and 5 to 3 in one DS helix b Complimentary nitrogenous bases match up with their partners A T G C 2 Made up of nucleotide monomers the nitrogenous bases A T G C sugar phosphate backbone and 5 carbon sugar a Nitrogenous bases are classified into two groups i Purines have two ring structures ii Pyrimidine only have one ring structure ii iii Who discovered it 1 Key scientists a Hershey and Chasei Determined that our genetic material is DNA not protein ii Used radioactive sulfur proteins and phosphorus DNA to determine what happens to protein and DNA in T2 bacteriophage 1 Labeleda proteins S b DNA P iii Results of the experiment 1 Phage DNA not protein entered host bacterial cells 2 Deciding factor E coli released newly made viruses that contained radiolabeled phosphorus DNA a Resulting in the find that DNA IS OUR GENETIC MATERIAL b Chargoffi Analyzed the base composition of various organisms ii Results 1 Genetic diversity among organisms DNA base composition differs between species 2 Chargaoff s rule base pairing a A bonds with T b G bonds with C 3 Adenine Guanine Thymine Cytosine means pairing 4 Provided further evidence that DNA is our genetic material and helped explain the structure of DNA once it was determined c Franklin Watson and Cricki Franklin had X ray crystallography data that indicated DNA is a double stranded helix of a specific width She also wrote a report with her model having the bases in the interior of the DNA molecule ii Watson and Crick put together data from various scientists including Franklin and Chargaff iii They found the structure of DNA doubled stranded helix therefore providing an explanation for its replication 1 NEEDED STRUCTURE TO KNOW ITS FUNCTION iv Structure most DNA molecules consist of two strands of DNA are held together by hydrogen bonds to form a double helix 1 2 Parent molecule template to create a daughter strand 3 Consists of Nucleic Acids the monomer is nucleotide a DNA nucleotide Sugar phosphate backbone the purple ribbons aka back of each strand b Nitrogenous bases TACG Bases inner part of strands i A T G C ii Antiparallel 4 Replication of DNA a It all starts at the origin of replication b Semi conservative accepted model c i First step Parental molecule used as template to produce daughter strands ii Second step separation of parental strands into templates iii Third step formation of new strands complementary to template Each backbone separates from the other to form a complimentary daughter strand so one parent molecule productions 2 daughter strands d Origin of Replication in E Coli i ii Small circular genomes with a single origin of replication e Origin of replication in a Eukaryotic cell i Linear genome with multiple origins of replication ii 1 Tip of bubble is origin of replication where the replication process begins in each bubble f Key players i Proteins ase enzyme 1 Helicase separates parental strands of DNA 2 Single stranded binding protein binds to single strand to keep parent strands separate 3 Toposisomerase Relieves supercoiling preventing the DS helix from getting too winded up 4 Primase Lays down an RNA primer 5 a Leading strand i Goes into the fork ii Continuous iii Requires only one primer iv Order of enzyme work v Primase vi Dpol III vii DPol I viii Ligase b Lagging strand i Goes away from the fork ii Discontinuous iii Requires many primers iv Okizawkie fragments v Order of enzyme work vi Primase Waiting game these vii DPol III repeat viii DPol I ix Ligase ii DNA polymerase III Dpol III Lays down DNA nucleotides at free 3 end using a pre existing strand of nucleotides to create polymer 1 Can only attach new nucleotides to free 3 end 2 Synthesize DNA to a 5 to 3 direction so 3 is constantly being elongated 3 Cannot start from scratch he requires a RNA primer AKA primase to get started iii DNA polymerase I Dpol I Removes RNA big diff between DPol I and III primer and replaces it with DNA nucleotides just lays new nucleotides down doesn t connect them needs ligase 1 Need ligase to attach sugar phosphate backbone of new DNA to preexisting chain it connects these two pieces iv Ligase Connects sugar phosphate backbones v 5 Proofreading and repaira Mismatch is detected by enzymes then Nuclease comes in to remove region then Dpol replaces nucleotides then ligase comes in and connects backbone of new regions with preexisting sides i Nuclease removes damaged region
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