With the aid of an example, describe a mechanism of antibiotic resistance.

(B)   Crystal violet stains bacteria very strongly to provide excellent contrast.  The slide will have been washed before placing under the microscope and the dye did not wash out.  What type of staining technique has been used in this case and which structural features of bacteria best explain why crystal violet is a good choice for this type of staining.

[4 marks]

A microscope is set up for you to view a slide using the x100 objective and oil immersion.  The slide contains a sample of bacteria that have been fixed and stained with the cationic dye Crystal Violet.  This is what you see:

(A)   Using terminology that is consistent with the norms of the discipline, describe what you see.     [3 marks]

In affinity chromatography, what role does the elution buffer play? 

A section of kidney tissue from a renal biopsy from a mouse has been stained with an antibody against complement component 3 (C3), linked to a green fluorophore—fluoroscein isothiocyanate (anti-C3-FITC).  As shown in the image below, C3 is expressed throughout the renal tissue from this mouse.

Section of mouse renal tissue stained with anti-C3-FITC

Which of the following species would be appropriate for the anti-C3 antibody to have been raised in? [pick one or more options]

Leptospirosis is a zoonotic disease (spreads from animals to humans) caused by different serovars of the bacterium Leptospira interrogans.  You are a vet who has been treating a lot of animals lately with the disease.  You are not feeling very well, you see your GP who takes a blood sample and sends it off to look for IgM antibodies to L. interrogans  (the presence of antibodies would mean you have leptospirosis). The lab uses an agglutination assay to detect IgM antibodies to L. interrogans (they use latex beads coated with a specific antigen to L interrogans and mixes it with the serum sample from the patient).  

Your sample is shown in panel A.  Do you have leptospirosis?

You are studying expression of the pro-apoptotic protein p53 in different cells lines.  You lyse a sample of each cell line, separate the proteins by SDS-PAGE and then probe the gel with an anti-p53 antibody; an anti-alpha actin antibody is also used to probe the membrane.  The results from the Western blot are shown in the figure below:

Explain what is shown by these results and be sure to address both p53 and alpha-actin.

An ELISA is used to detect IgM antibodies in people infected with the measles virus.  The plate is coated with measles virus antigens and patient serum is added to the wells. 

In the ELISA shown below, serum from 6 different patients has been tested for measles IgM antibodies.

Which one of the following statements is a correct interpretation of the ELISA result shown above?

You are going to complete a series of experiments to determine the number of cells in a population that are either CD4⁺ or CD8⁺.  You have the following reagents at your disposal:

• Anti-CD3-FITC (green)
• Anti-CD4-APC (red)
• Anti-CD8-PB (blue)

(FITC, fluorescein isothiocyanate; APC, allophycocyanin; PB, pacific blue)

For the purposes of this task, you will need to decide what your results will be (i.e. what proportion of the cell population will be CD3, CD4 or CD8 positive).  Draw and label (axes and give population %s) a flow cytometry histogram like the one below to display your results.  You can draw more than one histogram.

Take a photo/screenshot to upload an image of your "results" for this question.