THE MOLECULAR BASIS OF INHERITANCE I. History A. Discovery of “transformation” – a substitute in genotype and phenotype due to the uptake of palpeffectual DNA by a cell 1. Griffith 1920s did experiments after a conjuncture Streptococcus pneumoniae (p294 fig16. 2) a. took two filtrates of S. pneumoniae, one morbific, one not b. ardor killed morbific filtrate, then adulterated them after a conjuncture the subsistence nonmorbific filtrate c. subsistence nonmorbific filtrate became morbific d. nonmorbific filtrate took on morbific filtrate’s DNA ? became morbific e. see p294 fig16. 2 S filtrate = morbific, R = nonmorbific f. ventually Griffith’s effort control way to past studies on DNA substance the conveyance of genetic info. B. Demonstration that viral DNA and not viral protein contains genetic notification to effect past viral bisecticles 1. Hershey and Chase 1950s p295 fig16. 4 a. knew that banees could defile bacteria and effect past banees using the army cell’s replicating ‘machinery’ b. endground: sulfur gets incorporated into bane’ protein/phosphorus into bane’ DNA c. took T4 (bacteriophage) and plated after a conjuncture a lawn of E. coli and radioactively labeled sulfur, outcome = T4 after a conjuncture radioactive labeled protein (DNA not labeled) d. took T4 and plated after a conjuncture E. oli and radioactively labeled phosphorus = T4 after a conjuncture radioactively labeled DNA (protein not labeled) e. endground: when bane + bacteria is spun down, viral bisecticles in supernatant and bacteria in pellet f. took T4 (S-labeled) defileed new E. coli lawn, spun down, root S-radioactive labels in supernatant g. took T4 (P-labeled) defileed new E. coli lawn, spun down, root P-radioactive labels in pellet h. outcome = it’s the DNA that’s injected into the army to effect past bane (well-balanced plated these spun down pellet bacteria, and they lysed and released new bane C. Discovery of the construction of DNA 1.
Watson and Crick a. used an x-ray crystallography reintroduce (p297) by Franklin to enumerate DNA as a inclose-helical construction b. re-examination p298 – A pairs after a conjuncture T and G after a conjuncture C/ A and G are purines and C and T are pyrimidines/incimperil hydrogen bonds betwixt A and T, and triple betwixt G and C II. DNA Rejoinder A. 3 moulds of DNA rejoinder p300 fig 16. 10 1. Undestroyed mould – the parental helix splits, copies, then goes end concomitantly frequently to tarry uncontaminated conjuncture a cooperate entirely new observation is made 2. Semiundestroyed mould – the parental helix splits, copies and tarrys a bisect of the two new helixes 3.
Dispersive mould – the parental helix splits unevenly, copies and tarrys a bisect of the two new helixes but in pieces B. Experimental demonstration p300 fig16. 11 1. pretended radioactively labeled stolid nitrogen to replicating bacteria, then placed this culture into radioactively labeled active nitrogen (used to discover seacoasts) 2. allowed bacteria to involve frequently, outcomes gave mongrel DNA seacoasts (determined out undestroyed mould) (note: twain mongrels half and half and entirely adulterated appear the identical, so semiundestroyed and dispersive moulds twain upheld this time- see under) 3. llowed bacteria to involve frequently, outcomes gave mongrel seacoasts and singly active incimperil seacoasts (determined out dispersive mould gone all should be adulterated if this was suitable) C. Origins of rejoinder p301 fig16. 12 1. spring of rejoinder – plight where DNA rejoinder arises a. proteins avow a restricted posteriority on the template DNA, notorious the dsDNA to effect a fancy, and amelt rejoinder b. rejoinder fork – subsidence on DNA seacoast where new DNA seacoast is amplifying 1. prokaryotes plasmid (solitary spherical dsDNA helix) keep one spring of rejoinder and rejoinder occurs in twain superscriptions 2. ukaryotes keep rectirectilinear dsDNA keep frequent springs and rejoinder occurs in twain superscriptions D. Elongation of new DNA 1. DNA polymerase – enzyme that synthesizes the new DNA seacoast by adding nucleotides to the amplifying seacoast 2. DNA polymerase receives immateriality to do this by nucleotides substance nucleoside triphosphate (CTP, GTP, ATP, TTP) gone they imperil Pii = exergonic reaction to provide immateriality E. DNA is antiparallel p302 1. carbon numbering – carbon immoveffectual to worthiest is 1’, sum clockwise, carbon immoveffectual to phosphate cluster is 3’, carbon immoveffectual to other phosphate cluster is 5’ 2. be effectual to invent 5’ vs 3’ end . (p302 fig 16. 14) rejoinder occurs 5’ ? 3’, so seacoast substance made in this superscription is denominated the controling seacoast and rejoinder occurs toward the rejoinder fork 4. behindhand seacoast is rejoinder that occurs 5’ ? 3’ but rejoinder moves afar from the rejoinder fork a. behindhand seacoast produces Okazaki litter which must be united after a conjuncture DNA ligase p303 fig 16. 15 F. Priming DNA structure (getting rejoinder launched) p303 fig16. 15 1. primer – strong RNA polynucleotide on the template DNA seacoast gone DNA polymerase cannot true set-on-foot adding new nucleotides on its own a. rimer is laid down by enzyme primase b. singly one primer required for controling seacoast to amelt synthesizing/new RNA primer required for each behindhand seacoast arisening c. DNA polymerase well-balancedtually supplys RNA nucleotides after a conjuncture DNA ones and occurs anteriorly ligase connects any behindhand DNA seacoasts G. Other helpful proteins 1. helicase – enzyme that unwinds dsDNA at the rejoinder construct 2. solitary-seacoast restraining proteins – await abisect template DNA conjuncture rejoinder occurs **FINAL GOOD SUMMARY P304 fig 16. 16 III. DNA Proofreading and Repair
A. Mismatch restore 1. as DNA polymerase lays down nucleotides, if it notices a mismatched one to template, obtain transport and supply after a conjuncture redress one 2. Excision restore p305 fig16. 17: consists of nuclease – enzyme that can cut out injured segments of a DNA seacoast, then new nucleotides are populated in worthiestd on what the other DNA seacoast posteriority is by DNA polymerase and ligase IV. Rejoinder of the ends of DNA seacoasts p306 fig16. 18 A. DNA polymerase can singly add nucleotides to a 3’ end (gone it amplifys in a 5’ ? 3’ superscription) B.
For behindhand seacoast, there is no completion gone it supplys RNA primer and joins DNA after a conjuncture ligase C. For controling seacoast, there is a completion, gone the 3’ end of the template seacoast has a RNA primer, which cannot be supplyd after a conjuncture DNA nucleotides (by DNA polymerase) gone there is no 3’ end to set-on-foot from (DNA polymerase cannot true add nucleotides oppoplight of the DNA template seacoast – must use a RNA primer) D. This outcomes in successive involved seacoasts graceful limiteder and limiteder – the reparation? E. Telomeres – eukaryotic cells keep limited repetitive nucleotide posterioritys that do not rule for everything 1. elomeres vindicate the cell from deceptive alarms that there is DNA loss and agent the cell to die gone losing these ends don’t average everything (melody that prokaryotes do not keep this completion gone their DNA is spherical after a conjuncture no “end”) 2. but when telomeres are lost, are they supplyd? Yes by telomerase – enzyme that efforts in union after a conjuncture DNA polymerase to add tediousness to telomeres a. p306 fig16. 19 keep limitedened “true made” DNA seacoast b. telomerase is associated after a conjuncture an RNA seacoast and DNA polymerase c. telomerase verses up the RNA seacoast after a conjuncture the 3’ DNA seacoast to forward as a template to keep the 3’ end amplify d. hen the RNA seacoast forwards as a primer for new amplifyth onto the 5’ seacoast, then the primer is transportd e. outcome is an elongated DNA seacoast that was limiteded during rejoinder *telomerase is not introduce in most cells of multicellular organisms (love us) *DNA of older people tends to be limiteder *telomerase is catholic in seed verse cells – those that furnish melt to gametes *researchers invent telomerase in cancer cells – effects sagacity gone these cells involve repeatedly and would keep very limited DNA (feasible cancer therapy is to target their telomerase)