Lec9Notes - 10/5/10 Last time. Molecular basis of heredity...

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10/5/10 1 Molecular basis of heredity & DNA replication Principles of Biology Lecture 9 Prof. David Fitch Redox reactions in catalysis (glycolysis & citric acid cycle) power the production of ATP (oxidative phosphorylation) Feedback inhibition or stimulation regulate key enzymatic steps Regulation is direct, at the level of enzymes and substrates Last time. .. Regulation DNA is the basis for inheritance in most systems DNA structure primary sequence = information double helix and base complementarity = means of copying information DNA replicates "semiconservatively" (new DNA is ½ parental) DNA replication occurs 5'-to-3' this constraint imposes a problem in replicating the "lagging" strand DNA replication involves many components unwinding and opening of the replication fork at the origin(s) RNA primer elongation by DNA Pol III Okazaki fragments due to lagging strand synthesis removal of RNA primer and replacement with DNA by Pol I ligation of nascent DNA segments (DNA ligase) DNA mutations have consequences if not repaired Today's lecture Frederick Griffith (1928) Streptococcus pneumoniae R strain is "transformed" by killed S strain Living S (control) cel s Living R (control) cel s Heat-kil ed (control) S cel s Mixture of heat-kil ed S cel s and living R cel s Mouse dies Mouse healthy Mouse healthy Mouse dies Living S cel s are found in blood sample. Frederick Griffith in 1936 Bacterial transformation What is the transforming agent? Hypothesis 1: the polysaccharide coat of the S strain Hypothesis 2: some protein of the S strain Hypothesis 3: RNA Hypothesis 4: DNA Hypothesis 5: something else (none of the above) Which kind of experiments would discriminate between these hypotheses? A . Fractionate (extract) different kinds of molecules and use to transform cells. B . Use enzymes to degrade a particular type of molecule and see if the mixture fails to transform cells. C . Both of the above. D . None of the above. Design an experiment
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10/5/10 2 Oswald Avery, Maclyn McCarty, and Colin MacLeod (1944) (Rockefeller Institute, NYC) Polysaccharide coat did not transform R cells Only DNA-containing fraction transformed R cells Trypsin or RNase did not abolish transformation Only DNase destroyed this agent Thus, DNA was probably the transforming agent Avery in 1940; MacLeod & McCarty in 1965 Streptococcus pneumoniae DNA is the transforming agent Hershey & Chase (1952) (Cold Spring Harbor Laboratory, NY) Which component of T2 bacteriophage is required for T2 reproduction? T2 is made of protein + DNA Alfred Hershey (1972) & Martha Chase (1953) Phage head Tail Tail fiber DNA Bacterial cell 100 nm 1969 What is responsible for heredity? What are the correct predictions?
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Lec9Notes - 10/5/10 Last time. Molecular basis of heredity...

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