discuss the concepts of relative risk and absolute risk as applied to eating day to day foods. Use examples from the HERP values to dicuss. For example, red meat, particularly meat cured with nitrites, is a Class 1 carcinogen according to the World Health Organisation

What is the difference between virus attachment events and virus entry events that occur at the cell surface?

Describe the Kirby-Bauer test. What is it used for? How is it significant in the world of microbiology? Give examples of how to use the information it can give you.

17. The soil bacterium Pseudomonas fluorescens (taxid:294) is heavy metal tolerant and can survive in industrial waste and degrade and detoxify diverse organic pollutants.

You obtain Pseudomonas fluorescens ATCC 13525 which is sensitive to ampicillin (Ap), streptomycin (Sm) and spectinomycin (Sp) but resistant to chloramphenicol (Cm) and nalidixic acid (Nx). This strain is also lacZnegative (devoid of β-galactosidase activity).

You also obtain a donor Escherichia coli strain containing an ampicillin (Ap) resistant suicidal plasmid carrying the minitransposon mTn5-lacZSmSp  (this mTn5 has a promoterless lacZ and expresses Sm and Sp resistance). This strain is not resistant to any other antibiotics.

Consider in this case that cells can develop resistance to each antibiotic gene through spontaneous mutation at the frequency of 1 in 10⁶ cells.

You conjugally mate 10⁹ cells of ATCC 13525 with 10⁹ cells of the E. coli donor strain to construct random mTn5 mutations and identify molecular determinants for cadmium resistance.

1. What combination of antibiotics would you use in the media to select specifically for ATCC 13525::mTn5-lacZSmSp transconjugants and prevent the growth of spontaneous antbiotic resistant mutants?                                                       

2. To prevent secondary mutations from plasmid insertion, you would need to ensure the transconjugant cells had lost the delivery plasmid. How would you confirm the delivery plasmid was no longer present in these mutants?                        (1 mark)

You then replica patch transconjugants onto media containing the chromogenic substrate X-Gal in the presence and absence of cadmium. The following table shows the phenotypes of selected transconjugants.

c. Which mutant(s) have insertions in genes essential for cadmium resistance?

d. Which mutant(s) have insertions in genes up-regulated by cadmium?

e. Which mutant(s) have insertions in genes down-regulated by cadmium?

f. Which mutant(s) have insertions in genes that are constitutively expressed?

g. Which mutant(s) have insertions in genes that are not expressed in both the absence and presence of cadmium?

h. The DNA flanking the mTn5-lacZSmSp mutation was cloned from the cadmium sensitive mutant and the following sequence was obtained for the coding strand:

         5’.. GGCAGCACCAGCAAGG mTn5-lacZSmSp CCAGCAAGGTCAGCA..3’

Using this sequence provided, reconstruct the wild-type sequence

i. Provided with the information that the 5’ second base (underlined) in the provided sequence is the first base of a codon, provide the wild-type amino acid sequence of this portion of the protein and identify the amino and carboxyl termini.

j. Using the established amino acid sequence and the BLAST algorithm, what is the E value and the accession number of the highest scoring hit that aligns in the NCBI GenBank database?

k. What can you deduce to be the function of the protein based on the alignments obtained using the BLAST algorithm? (1 mark)

The Great Sperm Race Questions

1.What dangers/difficulties do the sperm face in the uterus?

2. How do sperm in the fallopian tube find the egg?

3. How does the female body help the sperm find the opening to the fallopian tube?

4.

What is one way that a mutation in the gene encoding for a wild type protein that generally binds ligands, prevent this protein from ligand binding?

What is the relationship between the amount of DNA condensation and the level of transcription?

Due to system limitations you are attempting to clone a small bacterial gene using a poorly characterised bacterial plasmid. You know that the plasmid contains only two drug resistance markers (one for resistance to tetracycline, another for resistance to ampicillin). You have determined that the restriction enzymes EcoRI and BamHI each cut the plasmid only once while SauIII and RsaI cut the plasmid twice. You also have determined that the EcoRI and SauIII recognition sites are within the tetracycline resistance marker, but the BamHI and RsaI recognition sites are not within or even close to either drug resistance marker. You must use this particular vector: a. Which restriction enzyme(s) should you use and why? b. What will happen if you use the BamHI recognition site? What will happen if you use the RsaI recognition site? (Describe this with regards to the functioning of the drug resistance marker and which antibiotic(s) you should use in the media)

Sketch 2 curves on the same graph for mammalian cells: after X-rays and after alpha-particles irradiation. Explain quantitatively the dependence on radiation dose of the survival for X-ray curve at low doses (up to 0.5Gy), at very high doses (higher than 7Gy). Discuss the mechanisms involved in cell death.

What more information is required to answer this question ?

In your own words state why the diseases that generally result from dysfunctional secretory pathway proteins are neurological disorders? In your answer explain the goal of the secretory pathway as you understand it and how it impacts neuronal function.

Describe how the Lac operon works. Be sure to include all the key elements: the components, the process, and the result.

A typical concentration of ampicillin used for bacterial selection in liquid LB is 100 microliter/mL. we prepared a 100 mg/mL ampicillin stock solution for your use. if you will only use .5 mL of your prepared dilution to spread on a plate, what is a reasonable volume of each dilution to prepare? Do you really need hundreds of milliliters?

Explain the term semiautonomous and the developmental relationships between the various plastid types – “how they are formed, what stimulates their formation”.

Question 3

Read the following three statements and then answer the question below.

• In 2019, the UK lost its ‘measles-free’ status.
• The basic reproduction number for measles (R0) is given as between 12 and 18, in different studies.
• The immunisation rate in the UK for measles dipped to a low point in 2003 to 80% coverage and since then has risen to 91% in 2019.

Question 5

1. Your friend is suffering from a fever and respiratory symptoms. She visits her GP and requests antibiotics. Explain why antibiotics may not be appropriate for her infection.
2. Describe the effects of the overuse of antibiotics on the bacterial population in humans.
3. In order to distinguish between viral and bacterial infections some GPs now use a rapid point-of-care (POC) test for levels of C-reactive protein (CRP). Explain the role of CRP in the immune response and its relevance to use in this test.
4. In a hospital setting, treatment with antibiotics is a risk factor for infection with Clostridium difficile. Explain why Clostridium difficile is commonly acquired in hospitals.

Explain, using calculations, the causal link between these three statements and briefly discuss whether there is any prospect of the UK regaining its ‘measles-free’ status in the next 5 years.

Question 6

1. The cytokine IFNγ is produced by Th1 cells. Outline three different functions of IFNγ in inflammation and/or the immune response.
2. Name one cytokine that is produced specifically by Th2 cells and state what effect it has on its target cell(s).
3. What advantage is there for the host in having two distinct patterns of immune response, controlled by Th1 and Th2 cells?