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This 3 page Class Notes was uploaded by Vrena Puentes on Sunday October 18, 2015. The Class Notes belongs to BSC2010 at Florida State University taught by Steven Marks in Summer 2015. Since its upload, it has received 23 views. For similar materials see Biological Science 1 in Biology at Florida State University.
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Date Created: 10/18/15
101515 The Molecular Basis of Inheritance Overview Life s Operating Instructions James Watson and Francis Crick introduced an elegant doublehelical model for DNA structure DNA is the most celebrated molecule of our time Hereditary info in encoded in DNA DNA program directs the development of biochemical anatomical physiological and behavioral traits DNA is the material of genetics How do we know or did we nd out that DNA is actually the material of heredity The Search for the Genetic Material TH Morgan shows that genes are located on chromosomes These genes are responsible for inherited traits Therefore chromosomes are the material inherited from one generation to the next Chromosomes are made of two molecule types proteins and DNA Proteins DNA Poymers Poymer 20 diff monomers 4 different monomers Grif th asked Which is inherited DNA or Proteins Method Used 2 different strain of strep Pneummoniae bacteria S Cells pathogenic mice die R Cells nonpathogenic mice live Heat killed S Cells mice live Heat killed S Cells mixed w living R Cells mice die Heat treatment renders proteins nonfunctional and doesn t destroy DNA func on Grif th called this phenomenon transformation now de ned as a change in genotype and phenotype due to assimilation of foreign DNA The application of heat irrevocably disrupts protein function but not DNA function What aspect of macromolecule structure do you think is most disrupted by heat Hydrogen bonds Evidence that viral DNA can program cells More evidence for DNA as the genetic material came from studies of viruses that infect bacteria Viruses called bacteriophages viruses that infect bacteria are used in molecular genetics research Viruses are a combo of protein and nucleic acid DNA especially Link between viruses heredity After viral infection a cell produces more of the same viruses The bacteriophage viruses can pass their own inherited material to infected cells Which one DNA or protein is passed to the infected cell Radioactive labeling proteins are labeled S35 and DNA is labeled P32 You can detect this as they undergo their radioactive decay they give off energy particles Proteins contain Sulfur hence the S DNA contains Phosphorus hence the P Additional Evidence that DNA is the Genetic Material It was known that DNA is a polymer of nucleotides each consisting of a nitrogenous base a sugar and a phosphate group In 1950 Erwin Chargaff reported that DNA composition varies from on species to the next DNA Structure Doube stranded CG GC CG TA AT CG GC This is some of the original data that Chargaff collected in 1950 Why do you think that the percentages for A and T are similar but not exact The actual percentages are exact but the data is not perfect Two ndings became known as Chargaff s rules 1 The base composition of DNA varies btwn species 2 In any species the number of A and T bases are equal and the number of G and C bases ae equal Franklin s xray crystallographic images of DNA enabled the deduction that the DNA molecule was a double helix Two linear strands coiled around each other Watson and Crick built molecules of a double helix to conform the xrays and chemistry of DNA Watson built a model where the backbones were antiparallel If a doublestranded DNA sample were composed of 10 thymine what would be the percentage of guanine 40 The direction of linear DNA molecules Conventionally written 5 l 3 5 T G C A 3 so there must be 3 A C G T 5 3 Carbon OH attached 5 Carbon P04 attached DNA provides directions for its own replication DNA directs synthesis of mRNA and thru mRNA controls protein synthesis Protein synthesis occurs on ribosomes
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