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To analyze:
Considering the results of
Introduction:
Meselson and Stahl performed an experiment to identify the mechanism of DNA replication in any known or unknown organism. In this experiment, an organism that possessed double stranded DNA was allowed to grow on a medium containing
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Genetic Analysis: An Integrated Approach (2nd Edition)
- Kornberg and his colleagues incubated soluble extracts of E. coli with a mixture of dATP, dTTP, dGTP, and dCTP, all labeled with 32P in the alpha-phosphate group. After a time, the incubation mixture was treated with trichloroacetic acid, which precipitates the DNA but not the nucleotide precursors. The precipitate was collected, and the extent of precursor incorporation into DNA was determined from the amount of radioactivity present in the precipitate. (a) If any one of the four nucleotide precursors were omitted from the incubation mixture, would radioactivity be found in the precipitate? Explain within 2 sentences. (2) (b) Would 32P be incorporated into the DNA if only dTTP were labeled? Explain within 2 sentences. (2) (c) Would radioactivity be found in the precipitate if 32P labeled the β or γ phosphate rather than the α phosphate of the deoxyribonucleotides? Explain within 2 sentences. (2)arrow_forwardApproximately how many high-energy bonds does DNA polymerase use to replicate a bacterial chromosome (ignoring helicase and other enzymes associated with the replication fork)? compared with its own dry weight of 10–12 g, how much glucose does a single bacterium need to provide enough energy to copy its DNA once?arrow_forwardFor each of the following ( A & B ) provide the method of transfer and a brief explanation as to why the method would not take place under the conditions described . 1. Which method of DNA transfer between bacteria would not take place if the donor and recipient were separated by a filter with a pore size of 0.45 um or another physical barrier 2. Which method of transfer would be blocked by the presence of high concentrations of DNAase ( enzymes capable of degrading DNA ) ?arrow_forward
- Consider the ends of the DNA fragments shown below. They have been produced by digestion of a single sequence of DNA using a number of restriction endonucleases. 1. 5'A 3' 3'TTCGA5' 2. 5'G 3' 3'CAGCT5' 3. 5'AATTC3' 3' G5 4. 5'TCGAC3' 3' G5' 5. 5'GGG 3' 3'CCC 5' Which of these ends are capable of annealing and being joined by DNA ligase?arrow_forwardAn alternative to semi-conservative replication is conservative replication in which the parent strands come apart only temporarily to serve as templates for synthesis of daughter strands but then come back together again as they were originally and the two new daughter strands then also form a duplex molecule. What single feature of the Meselsohn Stahl experiment allowed this conservative replication hypothesis to be rejected? (Hint:To answer this question you can consider the banding pattern produced on the cesium chloride density-gradient centrifugation following one round of replication in the Meselsohn Stahl experiment.)arrow_forwardWhich of the DNAs shown in Figure would move fastest during agarose gel electrophoresis?arrow_forward
- whose properties suggest that they originated from transfer of foreign DNA into a bacterial cell.arrow_forwardSuppose Meselson and Stahl labelled bacterial DNA with heavy nitrogen (15N, a stable isotope) and with radioactive carbon (14C), then allowed the bacteria to grow two generations in the presence of light nitrogen and non-radioactive carbon. If they extracted the DNA from the second generation of bacteria and centrifuged it: how many bands of DNA would there be in the centrifuge tube, where would the bands be in the centrifuge tube (top/least dense to bottom/most dense), for each band, what fraction of the total DNA would it represent and … which bands would be radioactive?arrow_forwardRestriction endonuclease digestion of a DNA sequence yielded fragments of the following sizes: 1. 5.2 kb 2. 0.8 kb 3. 1.2 kb 4. 3.8 kb 5. 3.1 kb After gel electrophoresis, what would be the order in which these fragments would be found—the last fragment listed being furthest from the negative pole.arrow_forward
- The following image is of an agarose gel. If DNA samples were loaded to this gel and the electrophoresis experiment was started, explain what would happen and why.arrow_forwardWhat is the role of alcohol in extracting DNA? DNA is a polar molecule with an overall negative charge, and as such is not soluble in alcohol, and therefore precipitates. DNA is a polar molecule with an overall positive charge, and as such is not soluble in alcohol, and therefore precipitates. DNA is a non polar molecule with an overall negative change, and as such is soluble in alcohol, and therefore precipitates. DNA is a polar molecule with an overall positive change, and as such is soluble in alcohol, and therefore precipitates.arrow_forwardWith regard to the experiment described in Figure, The DNA extract was treated with DNase, RNase, or protease.Why was this done? (In other words, what were the researcherstrying to determine?)arrow_forward
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