Order ID 53563633773 Type Essay Writer Level Masters Style APA Sources/References 4 Perfect Number of Pages to Order 5-10 Pages Description/Paper Instructions
Problem 1
In 1993 Mahan et al. developed a genetic system to positively select for bacterial genes that are specifically induced when bacteria infect their host. With the pathogen Salmonella typhimurium, the genes identified by this selection show a marked induction in bacteria recovered from mouse spleen. The system is schematically described in Fig. 1.
The collection of Salmonella cells carrying the recombinant clones was injected into mice. After 3 days, Salmonella cells were collected from the mice and some of the recombinant clones harbored by the surviving bacteria were sequenced to identify genes. The cells were also plated on X-gal containing medium to determine if they express lacZ in vitro. The results are shown in table 1.
Table 1. Analysis of the colonies isolated from the infected mice
Gene identified Color of the colony on X-gal plates
spvA Blue ryeB White csrC Blue tviA Blue sucA Blue fixX Blue yaaU White
- Name the genes that may code for functions that are virulence factors.
Although this methodology was very promising, the results were somehow disappointing. There was reason to believe that many genes were not identified even when they were turned on inside the host. It was thought that the problem could be the lack of control the researcher has on the expression of the purA gene. Therefore, the system was modified replacing the promoterless purA by a promoterless cat gene (this gene codes for resistance to chloramphenicol). The new system proved much more efficient in identifying the genes that are turned on inside the host. A first experiment (Experiment A) was carried out by treating the infected mice with chloramphenicol to obtain a blood concentration of 15 microg/ml. This strategy led to the selection of same genes as the previous experiment. Another experiment (Experiment B) was planned to identify more virulence genes.
- Should Experiment B consist of treating the infected mice with a different concentration of chloramphenicol?
- If yes, should the concentration of chloramphenicol be higher or lower than 15 microg/ml? Briefly justify your answer.
- What do you think it will happen if you do not treat de mice with chloramphenicol?
- Which of the following Salmonella typhimurium strains should you use for Experiment B?
- typhimurium (wild type)
- typhimurium purA
Briefly explain what it would happen if you use the wrong choice. (suggestion: one sentence is enough)
Problem 2
Tn1111 has been recently confirmed to be a transposon that may be useful as tool for certain biotechnology research areas. To understand more about its biology an experiment was done to determine its characteristics with respect to selection of the target sites when it transposes to another plasmid. Fig. 1 shows a basic diagram of the mating out experiment to select colonies harboring pVK102::Tn1111 and primers that have been synthesized. After the transposition experiment plasmid DNA was purified from colonies that harbor pVK102::Tn1111 and used as template for PCR reactions using as primers VK1 + Tr1 and VK2 + Tr1 (see Fig. 1). The products of these reactions were analyzed by agarose gel electrophoresis. The results are shown in Fig. 2.
Fig. 1
- What do you conclude about the specificity of insertion of Tn1111? Can the transposon insert in both orientations with respect to a site in the target plasmid? Give a brief justification for each answer.
Problem 3
The aac(6’)-Ib gene, which codes for resistance to amikacin (Ak) and was cloned using a vector that includes the bla as selectable marker. The bla gene code for resistance to ampicillin (Ap). An experiment of random mutagenesis using the mutator E. coli strain XL1 Red was carried out as part of the characterization of the aac(6’)-Ib gene and its product. The procedure was the usual, plasmid DNA was used to transform XL1 Red cells. The transformants were cultured overnight, then plasmid DNA was extracted and used to transform XL1 Blue (wild type). The transformants were then analyzed to identify a) null aac(6’)-Ib mutants and b) thermosensitive aac(6’)-Ib mutants
For this the transformed XL1 Blue cells were plated at 30°C in Ap containing L agar plates.
These colonies were then analyzed by inoculating plates as described in Fig 1.
- Identify the null and thermsosensitive aac(6’)-Ib mutant(s)
Fig. 1. Analysis of mutants. Colonies growing in Ap containing L agar plates at 30°C were inoculated in plates containing either Ap or Ak and incubated at 30 or 42°C.
RUBRIC
QUALITY OF RESPONSE NO RESPONSE POOR / UNSATISFACTORY SATISFACTORY GOOD EXCELLENT Content (worth a maximum of 50% of the total points) Zero points: Student failed to submit the final paper. 20 points out of 50: The essay illustrates poor understanding of the relevant material by failing to address or incorrectly addressing the relevant content; failing to identify or inaccurately explaining/defining key concepts/ideas; ignoring or incorrectly explaining key points/claims and the reasoning behind them; and/or incorrectly or inappropriately using terminology; and elements of the response are lacking. 30 points out of 50: The essay illustrates a rudimentary understanding of the relevant material by mentioning but not full explaining the relevant content; identifying some of the key concepts/ideas though failing to fully or accurately explain many of them; using terminology, though sometimes inaccurately or inappropriately; and/or incorporating some key claims/points but failing to explain the reasoning behind them or doing so inaccurately. Elements of the required response may also be lacking. 40 points out of 50: The essay illustrates solid understanding of the relevant material by correctly addressing most of the relevant content; identifying and explaining most of the key concepts/ideas; using correct terminology; explaining the reasoning behind most of the key points/claims; and/or where necessary or useful, substantiating some points with accurate examples. The answer is complete. 50 points: The essay illustrates exemplary understanding of the relevant material by thoroughly and correctly addressing the relevant content; identifying and explaining all of the key concepts/ideas; using correct terminology explaining the reasoning behind key points/claims and substantiating, as necessary/useful, points with several accurate and illuminating examples. No aspects of the required answer are missing. Use of Sources (worth a maximum of 20% of the total points). Zero points: Student failed to include citations and/or references. Or the student failed to submit a final paper. 5 out 20 points: Sources are seldom cited to support statements and/or format of citations are not recognizable as APA 6th Edition format. There are major errors in the formation of the references and citations. And/or there is a major reliance on highly questionable. The Student fails to provide an adequate synthesis of research collected for the paper. 10 out 20 points: References to scholarly sources are occasionally given; many statements seem unsubstantiated. Frequent errors in APA 6th Edition format, leaving the reader confused about the source of the information. There are significant errors of the formation in the references and citations. And/or there is a significant use of highly questionable sources. 15 out 20 points: Credible Scholarly sources are used effectively support claims and are, for the most part, clear and fairly represented. APA 6th Edition is used with only a few minor errors. There are minor errors in reference and/or citations. And/or there is some use of questionable sources. 20 points: Credible scholarly sources are used to give compelling evidence to support claims and are clearly and fairly represented. APA 6th Edition format is used accurately and consistently. The student uses above the maximum required references in the development of the assignment. Grammar (worth maximum of 20% of total points) Zero points: Student failed to submit the final paper. 5 points out of 20: The paper does not communicate ideas/points clearly due to inappropriate use of terminology and vague language; thoughts and sentences are disjointed or incomprehensible; organization lacking; and/or numerous grammatical, spelling/punctuation errors 10 points out 20: The paper is often unclear and difficult to follow due to some inappropriate terminology and/or vague language; ideas may be fragmented, wandering and/or repetitive; poor organization; and/or some grammatical, spelling, punctuation errors 15 points out of 20: The paper is mostly clear as a result of appropriate use of terminology and minimal vagueness; no tangents and no repetition; fairly good organization; almost perfect grammar, spelling, punctuation, and word usage. 20 points: The paper is clear, concise, and a pleasure to read as a result of appropriate and precise use of terminology; total coherence of thoughts and presentation and logical organization; and the essay is error free. Structure of the Paper (worth 10% of total points) Zero points: Student failed to submit the final paper. 3 points out of 10: Student needs to develop better formatting skills. The paper omits significant structural elements required for and APA 6th edition paper. Formatting of the paper has major flaws. The paper does not conform to APA 6th edition requirements whatsoever. 5 points out of 10: Appearance of final paper demonstrates the student’s limited ability to format the paper. There are significant errors in formatting and/or the total omission of major components of an APA 6th edition paper. They can include the omission of the cover page, abstract, and page numbers. Additionally the page has major formatting issues with spacing or paragraph formation. Font size might not conform to size requirements. The student also significantly writes too large or too short of and paper 7 points out of 10: Research paper presents an above-average use of formatting skills. The paper has slight errors within the paper. This can include small errors or omissions with the cover page, abstract, page number, and headers. There could be also slight formatting issues with the document spacing or the font Additionally the paper might slightly exceed or undershoot the specific number of required written pages for the assignment. 10 points: Student provides a high-caliber, formatted paper. This includes an APA 6th edition cover page, abstract, page number, headers and is double spaced in 12’ Times Roman Font. Additionally, the paper conforms to the specific number of required written pages and neither goes over or under the specified length of the paper. GET THIS PROJECT NOW BY CLICKING ON THIS LINK TO PLACE THE ORDER
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