Presentation on theme: "Chapter 16 DNA & Replication. Slide 2 of 24 Bell Ringer 1. On a sheet of paper 2. Write down everything you know about DNA -- Who discovered DNA? -- What."— Presentation transcript:
Slide 4 of 24 The Beginnings T. H. Morgan’s group showed that genes are located on chromosomes The two components of chromosomes—DNA and protein— were candidates for the genetic material The role of DNA in heredity was first discovered by studying bacteria and the viruses that infect them The discovery of the genetic role of DNA began with research by Frederick Griffith in 1928
Slide 5 of 24 Griffin & Transformation Griffin looked at bacteria & mice Major finding = Transformation Killed disease-causing bacteria + live, harmless bacteria Result: Live, disease-causing bacteria Transformation – change in genotype and phenotype due to uptake of foreign DNA
Slide 6 of 24 Living S cells (control) Living R cells (control) Heat-killed S cells (control) Mixture of heat-killed S cells and living R cells Mouse dies Living S cells Healthy Mouse Mouse dies
Slide 7 of 24 Hershey & Chase What is responsible for transformation? Dumb question now, but not so at the time Bacteriophages – viruses than infect bacteria Consist of protein + DNA Which is the transformative agent?
Slide 8 of 24 EXPERIMENT Phage DNA Bacterial cell Radioactive protein Radioactive DNA Batch 1: radioactive sulfur ( 35 S) Batch 2: radioactive phosphorus ( 32 P)
Slide 9 of 24 EXPERIMENT Phage DNA Bacterial cell Radioactive protein Radioactive DNA Batch 1: radioactive sulfur ( 35 S) Batch 2: radioactive phosphorus ( 32 P) Empty protein shell Phage DNA
Slide 10 of 24 EXPERIMENT Phage DNA Bacterial cell Radioactive protein Radioactive DNA Batch 1: radioactive sulfur ( 35 S) Batch 2: radioactive phosphorus ( 32 P) Empty protein shell Phage DNA Centrifuge Pellet Pellet (bacterial cells and contents) Radioactivity (phage protein) in liquid Radioactivity (phage DNA) in pellet
Slide 11 of 24 Chargaff’s Rules In DNA: [A] = [T] & [G] = [C] Why would this be true?
Slide 13 of 24 Structural Model of DNA? M. Wilkins & R. Franklin use X-ray crystallography to study molecular structure Watson & Crick “deduced” that DNA was 2-stranded Double Helix
Slide 14 of 24 DNA Replication DNA DNA 2 strands separate, and each one is paired using complementary bases
Slide 15 of 24 Themes (meh.) Science as a process Regulation Interdependence in nature Science, Technology, & Society
Slide 16 of 24 Semiconservative Replication Each daughter molecule = 1 old strand (Conserved from parent strand) + 1 newly replicated strand Called Semiconservative Half of the strands are conserved from the parent Competing (Incorrect models): Conservative & Dispersive
Slide 21 of 24 Telomeres Eukaryotic chromosomal DNA molecules have at their ends nucleotide sequences called telomeres Telomeres do not prevent the shortening of DNA molecules, but they do postpone the erosion of genes near the ends of DNA molecules It has been proposed that the shortening of telomeres is connected to aging Telomerase – enzyme that lengthens the telomere Telomerase in cancerous cells?