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Lecture 2

BIOL 308 Lecture 2: Lecture 2 notes

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University of Waterloo
BIOL 308
John Heikkila

Functions of DNA 1: Store information: A sequence of bases with coding (tRNA, rRNA) and regulatory/enhancer regions (gene expression, not in promoter – maybe up/downstream or in introns) the produce functional RNA/protein 2: Replicate faithfully: Parental strands are a template for the complementary daughter strand semi conservatively. Information is preserved because one DNA strand can predict the sequence of the other 3: Can mutate: Which could alter the protein or regulatory process. There is co-linearity where the DNA codons dictate the order of amino acids in proteins. This allows for the formation of new alleles if not knocked out. If regulatory sequences are mutated, the gene might not express well or express too well since transcription factors need a specific set of AA’s to be bound to the promoter History Year Scientist Notes 1868 Friedrich Miescher ▪ DNA isolated from salmon sperm 1944 Oswald Avery, Colin ▪ Pathogenic strains are transferred through DNA MacLeod, Maclyn McCarty 1947 Erwin Chargaff ▪ A&T (2HB) and G&C (3HB) in DNA are close in number 1952 Alfred Hershey, Martha Chase ▪ T2 bacteriophage injects DNA into cells to make more bacteriophage 1952 Rosalind Franklin, Maurice ▪ X-ray crystallography of DNA to find its 3D model of the phosphate backbone and helical structure Wilkins 1953 James Watson, Francis Crick ▪ Double helix model of DNA: Right handed complementary antiparallel double helix, sugar phosphate negative backbone, bases were parallel and perpendicular to the molecule axes, 3.4nm apart with hydrogen bonds keeping purines & pyrimidines together 1958 Matthew Meselson, Franklin ▪ DNA replication occurs semi conservatively (preserved information) with a parental dpltwo Stahl identical daughter duplexes with preserved information ▪ Use E.coli in media with N15 (heavy) and grew it for generations so even DNA nitrogen had N15 and then transferred them to N14 media and allowed for DNA to replicate. When isolating, purifying, and centrifuging the DNA in CsCl (dense salt). N15 would sink, N14 would float, a combination would be in the middle – which was the result 1965 Francis Crick, Marshall ▪ Genetic code with codons coding for different AA’s: DN protein (co-linearity) Nirenburg, Philip Leder Central dogma ▪ DNA strands are: Double helix, complementary, antiparallel, and have polarity at the 5’PO4 and 3’OH ends ▪ Gene = All DNA sequences to code for functional RNA/protein products including coding and regulatory regions ▪ Transcription factors bind to the regulatory sequences and interact with RNA polymerase to activate transcription Template = Antisense strand (DNA like) Coding = Sense strand (RNA like) Models of DNA replication 1: Semiconservative: Each daughter DNA duplex has one old and one new strand (2 hybrid, 2 new) 2: Conservative: The new DNA duplex is completely new with the old DNA duplex reassembled (1 old, 3 new) 3: Dispersive: The parental duplex sections are randomly dispersed in the daughter strands (4 new with old parts) Types of mutations 1: Silent: A base change doesn’t affect the protein product 2: Missense mutation: The mutation changes the protein pr
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