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March 15, 2017 Monday, March 13, 2017 LT: I can explain how cell respiration is the process that provides energy for living organisms. Entry Task: What macromolecule(s) are broken down in the: mouth stomach small intestine Today: Written Test Continue Ch. 12.1 & 12.2 Reading/Notes March 15, 2017 Exit Task: What is DNA? March 15, 2017 Tuesday, March 14, 2017 LT: I can explain the structure and function of DNA. Entry Task: What is the base pairing rule in DNA structure? Today: DNA Extraction Lab Continue Ch. 12.1 & 12.2 Reading/Notes March 15, 2017 Exit Task: What kind of bond holds nucleotides together in a single strand? What kind of bond holds pairs of nucleotides together in a double strand? March 15, 2017 Wednesday, March 15, 2017 LT: I can describe the structure and function of DNA. Entry Task: What are the 3 roles of DNA in heredity? Today: Ch. 12.1 & 12.2 Reading Quiz Ch. 12.1 & 12.2 Notes March 15, 2017 The march to understanding that DNA is the genetic material Johann Miescher (1868) T.H. Morgan (1908) Frederick Griffith (1928) Avery, McCarty & MacLeod (1944) Erwin Chargaff (1947) Hershey & Chase (1952) Rosalind Franklin (1952) Watson & Crick (1953) Meselson & Stahl (1958) March 15, 2017 Johann Miescher - 1868 Wanted to identify chemical composition of nucleus Isolated acidic compound that contains nitrogen and phosphorous March 15, 2017 Genes are on chromosomes 1908/1933 T.H. Morgan • working with Drosophila (fruit flies) • genes are on chromosomes • but is it the protein or the DNA of the chromosomes that are the genes? Key factor in determining the genetic material was choosing appropriate experimental organisms (bacteria and the viruses that infect them) March 15, 2017 Frederick Griffith - 1928 · Streptococcus pneumonia bacteria was working to find cure for pneumonia, worked with pathogenic “S” strain and harmless “R” strain · harmless live bacteria mixed with heat-killed infectious bacteria causes disease in mice · substance passed from dead bacteria to live bacteria = “Transforming Factor” · Transformation: a change in genotype and phenotype due to assimilation of foreign DNA March 15, 2017 Transformation? something in heat-killed bacteria could still transmit disease-causing properties March 15, 2017 DNA is the “Transforming Factor” - 1944 Avery, McCarty & MacLeod · purified both DNA & proteins from Streptococcus pneumonia bacteria which will transform live, non-pathogenic bacteria? · injected protein into bacteria no effect · injected DNA into bacteria transformed harmless bacteria into virulent bacteria Many biologists remained skeptical, mainly because little was known about DNA Conclusion? DNA is the transforming factor! March 15, 2017 Exit Task: What is true about the relationship between bases A - T & G - C in any species? March 15, 2017 Thursday, March 16, 2017 LT: I can describe the structure and function of DNA. Say hello to Baby Denman! His development is brought to you by DNA:) Entry Task: How did Avery, et al, prove that DNA was the transforming factor? Today: Ch. 12.1 & 12.2 Notes Build a Model of a DNA Molecule March 15, 2017 Confirmation of DNA - 1952/1969 Hershey & Chase • classic “blender” experiment • worked with bacteriophage T2 viruses that infect E.coli bacteria • grew phage viruses in 2 media, radioactively labeled with either 35S in their proteins 32P in their DNA • infected bacteria with labeled phages http://highered.mheducation.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/ 0072437316/120076/bio21.swf::Hershey+and+Chase+Experiment March 15, 2017 Blender experiment Radioactive phage & bacteria in blender · 35S phage radioactive proteins, phage parts remain suspended in the liquid therefore protein did NOT enter bacteria · 32P phage radioactive DNA stayed in pellet therefore DNA did enter bacteria · Confirmed DNA is “transforming factor” March 15, 2017 March 15, 2017 Chargaff - 1947 · DNA composition: “Chargaff’s rules” varies from species to species DNA is a polymer of nucleotides (phosphate, sugar, base) all 4 bases not in equal quantity bases present in characteristic ratio humans: A = 30.9% T = 29.4% G = 19.9% C = 19.8% Rules A=T C=G March 15, 2017 Maurice Wilkins and Rosalind Franklin: X-ray crystallography of DNA · Showed three things: DNA twisted, double stranded, nitrogen bases found in middle · Franklin’s X-ray crystallographic images of DNA enabled Watson/ Crick to deduce that DNA was helical and also the width of the helix and the spacing of the nitrogenous bases https://video.search.yahoo.com/video/ play;_ylt=A2KIo9Rr1BdX.xUAZoIsnIlQ;_ylu=X3oDMTByNDY3bGRuBHNlYwNzcgRzbGsDd mlkBHZ0aWQDBGdwb3MDNQ--?p=Rosalind +Franklin&vid=0c980bd00567aa840312f814a8724564&turl=http%3A%2F%2Ftse1.mm.bing.net %2Fth%3Fid%3DOVP.V5d56d607f279436519d23c7d65ef97df%26pid%3D15.1%26h %3D168%26w%3D300%26c%3D7%26rs%3D1&rurl=https%3A%2F%2Fwww.youtube.com %2Fwatch%3Fv%3DTZUun93_V18&tit=Rosalind+Franklin+-+My+Favourite +Scientist&c=4&h=168&w=300&l=296&sigr=11bgb5rgu&sigt=11a6msh04&sigi=1319vjppm&a ge=1290524777&fr2=p%3As%2Cv%3Av&fr=yhsmozilla-002&hsimp=yhs-002&hspart=mozilla&tt=b March 15, 2017 Structure of DNA Watson & Crick - 1953/1962 · developed double helix model of DNA · Inspired by 3 recent discoveries: Rosalind Franklin/Wilkins -X-ray Chargaff’s rules Linus Pauling – alpha helical structure of protein March 15, 2017 DNA Structure Monomer - nucleotide Outside - sugar and phosphate backbone - held together by covalent & phosphodiester bonds Inside - nitrogen bases (A, T, G, C) - held together by hydrogen bonds March 15, 2017 Different Base Pairs Purines Nitrogen bases made of double rings of carbon and nitrogen atoms Adenine (A) and Guanine (G) March 15, 2017 Different Base Pairs Pyrimidines Nitrogen bases made of single ring of carbon and nitrogen atoms Cytosine (C) and Thymine (T) March 15, 2017 Watson and Crick 2 Hydrogen bonds 3 Hydrogen bonds March 15, 2017 Build a Model of a DNA Molecule March 15, 2017 Exit Task: In DNA what type of bond(s) hold the phosphate/sugar backbone together and what type of bond(s) hold the nitrogenous bases together? March 15, 2017 Friday, March 17, 2017 LT: I can describe the structure and function of DNA. Entry Task: What is meant by the term "semi-conservative" replication? Cool Friday Thing! Today: Ch. 12.3 Notes DNA Replication Assignment March 15, 2017 Many proteins work together in DNA replication and repair · The relationship between structure and function is manifest in the double helix · Watson and Crick noted that the specific base pairing suggested a possible copying mechanism for genetic instructions · Since the two strands of DNA are complementary, each strand acts as a template for building a new strand in replication · In DNA replication, the parent molecule unwinds, and two new daughter strands are built based on basepairing rules March 15, 2017 Copying DNA · Replication of DNA base pairing allows each strand to serve as a template for a new strand March 15, 2017 Semi-conservative replication - 1958 Meselson & Stahl label “parent” nucleotides in DNA strands with heavy nitrogen = 15N label new nucleotides with lighter isotope = 14N March 15, 2017 DNA Replication Helicase enzymes break the hydrogen bonds between base pairs. March 15, 2017 DNA Replication The DNA unwinds like a zipper. We call the region where the separation is occurring the replication fork. March 15, 2017 DNA Replication As the DNA separates down the middle, DNA polymerase recombines adenine with thymine and guanine with cytosine. March 15, 2017 DNA Replication This creates an exact copy of the original DNA, even though each strand is providing a different template. Semiconservative - each new DNA molecule contains one old and one new strand. March 15, 2017 DNA Replication DNA polymerase can only synthesize in one direction (5′ to 3′), so each strand is replicated slightly differently. March 15, 2017 On the leading strand, DNA polymerase simply moves down the DNA molecule, attaching base pairs as the DNA continues unwinding. The synthesis of the new strand is continuous. Single strand binding proteins have the simple but important function of preventing the separated strands of DNA from reannealing (rejoining). March 15, 2017 On the lagging strand, DNA polymerase adds bases in small segments called Okazaki fragments after primase adds short RNA sequences called primers. The synthesis of the new strand is discontinuous. March 15, 2017 Completing DNA Replication · Once all of the bases are matched up (A with T, C with G), an enzyme called exonuclease strips away the primer(s). · The gaps where the primer(s) were are then filled by yet more complementary nucleotides. · The new strand is proofread to make sure there are no mistakes in the new DNA sequence. · Finally, an enzyme called DNA ligase seals up the sequence of DNA into two continuous double strands. https://www.youtube.com/watch?v=wCKF-2nqaOc March 15, 2017 Replicating the Ends of DNA Molecules For linear DNA, DNA polymerase cannot replicate or repair the 5' ends of the daughter DNA strands. Result is a shortening of the DNA molecule with each round of replication. Telomeres are repetitions (100-1,000) of short nucleotide sequences at the ends of DNA molecules that do not contain genes. This protects the organism's genes from being eroded. March 15, 2017