Biology And Biomedical Sciences BIOL 2960 Lecture Notes - Lecture 19: Single-Strand Dna-Binding Protein, Atp Hydrolysis, Pyrophosphate

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harlequinimpala978

13 Dec 2016

School

WUSTL

Department

Biology And Biomedical Sciences

Course

Biology And Biomedical Sciences BIOL 2960

Professor

Bednarski, Smith, Kundel, Gole, Kunkel, Majors, Hafer

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2 march 2016: dna replication, determining how dna replicates, messelson-stahl experiment, 1958 (to determine how dna replicated, approach- density labeling of dna. Grow a bacterial culture (e. coli) for many cell generations in a liquid medium containing a heavy isotope of nitrogen (15n) Collect a sample of culture at time=0 . Transfer the rest of the culture to a new liquid medium containing the common light isotope of nitrogen (14n) At various times after transfer (1 generation, 2 generations, etc. ) remove a sample of bacteria. Purify dna from samples and measure density via cesium chloride centrifugation: the density of the dna was measured by the equilibrium gradient after centrifugation. After adding purified dna to cscl and centrifuging for a long time, the cscl solution forms a gradient (high density and the bottom, lower density on top) A dna band will form at the exact density in the solution: expectations:

Related Questions

Assume that a culture of E. coli was grown for approximately 50 generations in 15N (provided in the medium in the ammonium ion), which is a heavy isotope of nitrogen (14N). You extract the DNA from the culture, and it has a density of 1.72 gm/cm3 (water = 1.00 gm/cm3), as determined by sedimentation velocity centrifugation. From the literature, you determine that DNA containing only the common form of nitrogen, 14N, has a density of 1.70 gm/cm3. Bacteria from the 15N culture were washed in buffer and transferred to 14N medium for one generation immediately after which the DNA was extracted and its density determined. What would be the expected density of the extracted DNA?

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Assume that a culture of E. coli was grown for approximately 50 generations in 15N (provided in the medium in the ammonium ion), which is a heavy isotope of nitrogen (14N). You extract the DNA from the culture, and it has a density of 1.72 gm/cm3 (water = 1.00 gm/cm3), as determined by sedimentation velocity centrifugation. From the literature, you determine that DNA containing only the common form of nitrogen, 14N, has a density of 1.70 gm/cm3. Bacteria from the 15N culture were washed in buffer and transferred to 14N medium for one generation immediately after which the DNA was extracted and its density determined. What would be the expected density of the extracted DNA?

You then heat the DNA until it completely denatured (95Â°C for 15 minutes), what would you expect the density of the DNA in the denatured extract to be following sedimentation velocity centrifugation? For the purposes of this question, assume that DNA has the same density regardless of whether it is single- or double-stranded.

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1) The semiconservative nature of DNA replication (as shown inFig. 3.9) was proposed by Watson and Crick in 1953, but it wasn'texperimentally verified until 1958. Meselson and Stahl grewbacteria on the âheavyâ nitrogen isotope N15, producing DNA thatwas denser than normal. The food source was then abruptly switchedto one containing only N14. Bacteria were harvested and the DNAisolated by density gradient centrifugation.

What is the density of the DNA of the first-generation daughterDNA molecules? Explain.

What is the density of the DNA isolated after two generations?Explain.

What results would Meselson and Stahl have obtained had DNAreplicated conservatively?

2) a. One form of the diseaseadrenoleukodystrophy (ALD) is caused by the substitution of serinefor asparagine in the ALD protein. List the possiblesingle-nucleotide alterations in the DNA of the ALD gene that couldcause this genetic disease. b. In another form ofALD, a CGA codon is converted to a UGA codon. Explain how thismutation affects the ALD protein.

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Biology And Biomedical Sciences BIOL 2960 Lecture Notes - Lecture 19: Single-Strand Dna-Binding Protein, Atp Hydrolysis, Pyrophosphate

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