AP Biology (An Introduction)

DNA & Replication

Bell Ringer1. On a sheet of paper2. Write down everything you know about DNA-- Who discovered DNA?-- What is the structure of DNA? -- How does DNA differ from RNA?

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Slide # of 24The BeginningsT. H. Morgans group showed that genes are located on chromosomesThe two components of chromosomesDNA and protein were candidates for the genetic materialThe role of DNA in heredity was first discovered by studying bacteria and the viruses that infect themThe discovery of the genetic role of DNA began with research by Frederick Griffith in 1928

Slide # of 24Griffin & TransformationGriffin looked at bacteria & miceMajor finding = TransformationKilled disease-causing bacteria + live, harmless bacteriaResult: Live, disease-causing bacteria

Transformation change in genotype and phenotype due to uptake of foreign DNASlide # of 24

Living S cells (control)Living R cells (control)Heat-killed S cells (control)Mixture of heat-killed S cells and living R cellsMouse diesLiving S cellsHealthy MouseHealthy MouseMouse diesSlide # of 24Hershey & ChaseWhat is responsible for transformation?Dumb question now, but not so at the timeBacteriophages viruses than infect bacteriaConsist of protein + DNAWhich is the transformative agent?

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EXPERIMENTPhageDNABacterial cellRadioactive proteinRadioactive DNABatch 1: radioactive sulfur (35S)Batch 2: radioactive phosphorus (32P)Slide # of 248Figure 16.4 Is protein or DNA the genetic material of phage T2?

EXPERIMENTPhageDNABacterial cellRadioactive proteinRadioactive DNABatch 1: radioactive sulfur (35S)Batch 2: radioactive phosphorus (32P)Empty protein shellPhage DNASlide # of 249Figure 16.4 Is protein or DNA the genetic material of phage T2?

EXPERIMENTPhageDNABacterial cellRadioactive proteinRadioactive DNABatch 1: radioactive sulfur (35S)Batch 2: radioactive phosphorus (32P)Empty protein shellPhage DNACentrifugeCentrifugePelletPellet (bacterial cells and contents)Radioactivity (phage protein) in liquidRadioactivity (phage DNA) in pelletSlide # of 2410Figure 16.4 Is protein or DNA the genetic material of phage T2?Chargaffs RulesIn DNA:[A] = [T] & [G] = [C]

Why would this be true?

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Slide # of 24Structural Model of DNA?M. Wilkins & R. Franklin use X-ray crystallography to study molecular structure

Watson & Crick deduced that DNA was 2-strandedDouble Helix

Slide # of 24DNA ReplicationDNA DNA2 strands separate, and each one is paired using complementary bases

Slide # of 24Themes (meh.)Science as a process

Regulation

Interdependence in nature

Science, Technology, & Society

Slide # of 24Semiconservative ReplicationEach daughter molecule = 1 old strand (Conserved from parent strand) + 1 newly replicated strandCalled SemiconservativeHalf of the strands are conserved from the parent

Competing (Incorrect models): Conservative & DispersiveSlide # of 24

Slide # of 24DNA Replication16_05DNAandRNAStructure

16_07DNADoubleHelix

16_09Overview

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Slide # of 24TelomeresEukaryotic chromosomal DNA molecules have at their ends nucleotide sequences called telomeresTelomeres do not prevent the shortening of DNA molecules, but they do postpone the erosion of genes near the ends of DNA moleculesIt has been proposed that the shortening of telomeres is connected to agingTelomerase enzyme that lengthens the telomereTelomerase in cancerous cells?

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PROKARYOTEEUKARYOTESlide # of 24