Rebecca DavenportBIOL 1406 BW110/27/16Ch 16 blueprint1. Molecular basis of inheritancea. 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 helixb. 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 Chase-i. 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. Labeled-a. proteins- Sb. DNA- Piii. Results of the experiment:1. Phage DNA, not protein, entered host bacterial cells2. Deciding factor**** E. coli released newly madeviruses that contained radiolabeled phosphorus (DNA). a. Resulting in the find that DNA IS OUR GENETIC MATERIAL!!!!b. Chargoff-i. Analyzed the base composition of various organismsii. Results:1. Genetic diversity among organisms- DNA base composition differs between species.2. Chargaoff’s rule: base pairinga. A bonds with Tb. G bonds with C3. % Adenine = % Guanine % Thymine = % Cytosine= <<<< means pairing4. Provided further evidence that DNA is our genetic material and helped explain the structure of DNA once it was determined.c. Franklin, Watson and Crick-i. 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 strand3. Consists of Nucleic Acids: the monomer is nucleotidea. DNA nucleotide: Sugar phosphate backbone- the purple ribbons aka back of each strand. b. Nitrogenous bases: TACG Bases- inner part of strandsi. A = T; G = Cii. Antiparallel4. Replication of DNA:a. It all starts at the origin of replication. b. Semi-conservative: accepted modelc.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 DNA2. Single-stranded binding protein: binds to single strand to keep parent strands separate.3. Toposisomerase: Relieves supercoiling, preventing the DS helix from getting too windedup. 4. Primase: Lays down an RNA primer5.a. Leading strand:i. Goes into the forkii. Continuous iii. Requires only one primeriv. Order of enzyme work:v. Primasevi. Dpol IIIvii. DPol Iviii. Ligaseb. Lagging strand:i. Goes away from the fork ii. Discontinuousiii. Requires many primersiv. Okizawkie fragmentsv. Order of enzyme work:vi. Primasevii. DPol IIIviii. DPol Iix. Ligaseii. 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 backboneof new DNA to preexisting chain, it connects these two pieces. Waiting game, theserepeat!!iv. Ligase: Connects sugar phosphate backbones.v.5. Proofreading and repair-a. 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
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