This preview shows page 1 out of 3 pages.
View Full DocumentEnd of preview. Want to read all 3 pages?
Upload your study docs or become a GradeBuddy member to access this document.
View Full DocumentBIOL-L 211 Lecture 8 Outline of Last Lecture I. ArticlesII. HistonesIII. The NucleosomeOutline of Current Lecture I. Replication HypothesesII. Meselson-Stahl ExperimentIII. Methods and Minutia of DNA ReplicationCurrent LectureReplication II. Replication HypothesesA. Dispersive Model: Proposed that parental DNA strands fragmented and then served as templatesB. Semiconservative Model: Proposed that DNA "unzipped," yielding two identical template strands which then served as templates for new DNA1. Watson and Crick (from earlier lectures) preferred this modelC. Conservative Model: parental strands of DNA remained together throughout replicationII. Meselson-Stahl ExperimentA. Purpose: Discover mechanism for DNA replicationB. Procedure:1. Bacteria grown in media with nucleotide precursors labeled with a heavy isotope of Nitrogen (15N)2. Bacteria then transferred to media with 14N precursors (light isotope)These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.3. Bacteria allowed to grow in 14N solution4. Three samples placed in ultracentrifuge through a CsCl gradienta. DNA now separated by density5. ObserveC. Results: After two generations, the semiconservative model proved to be accurateIII. Methods and Minutia of DNA ReplicationA. Origins of Replication1. Prokaryotes have ONE2. Eukaryotes have hundreds to thousands3. Pre-Replication Complex: melts DNA strands apart at origins of replicationa. Specialized proteins find the origins of replicationB. The Replication Fork1. DNA synthesizes in two directions: toward and away from the replication fork (but still 5'->3' both ways)a. Leading Strand: synthesized toward/with the replication forkb. Lagging Strand: synthesized piece (Okazaki fragment) by piece in the direction opposite the replication fork2. Helicases: rings that unwind DNA (requiring ATP hydrolysis)3. Primases: enzymes that add primers to single stranded DNAa. Primers: starting point for DNA synthesis4. Primer:template junction: Combination of primer and template stranda. Template Strand: DNA is synthesized based off of this strand5. DNA polymerase: enzyme that synthesizes DNA (it's like a hand!!)6. Topoisomerase: enzyme that relieves structural tensiona. Resolves positive supercoils: knot of DNA that builds up in front of replication forkb. Creates instead negative supercoils: which are a natural and good conformation of DNA7. Single-stranded DNA binding proteins (SSBs): bind newly separated DNA strands and keep ssDNAs apartC. DNA Polymerase (hand)1. Palm: catalyzes DNA synthesis and monitors base pairing2. Fingers: bend template strand and set up next base to be paired3. Thumb: ensures that DNA polymerase does not dissociate from DNAD. Deoxynucleoside Triphosphate (dNTP): dATP, dGTP, dCTP, dTTP1. Base pair connected to triphosphate group via a deoxyribose group2. The phosphates are labeled alpha, beta, and gamma respectively with regards to their proximity to the nucleoside3. To form a phosphodiester bond, the beta and gamma phosphates are removed (post attack of the alpha phosphate by the 3' OH of the primer)4. The template strand controls which dNTPs are
View Full Document
Unlocking...