ICAR AICE-JRF/SRF Veterinary and Animal Biotechnology: practice questions

1 · Molecular biology and recombinant DNA · medium

A student transforms 1 ng of plasmid into competent cells, adds recovery medium to a final volume of 1 mL, spreads 100 microlitres and counts 150 colonies. The transformation efficiency is:

1. 1.5 x 10^9 transformants per microgram
2. 1.5 x 10^5 transformants per microgram
3. 1.5 x 10^3 transformants per microgram
4. 1.5 x 10^6 transformants per microgram

2 · PCR and quantitative PCR · medium

A qPCR standard curve of ten-fold dilutions has a slope of -3.6. The amplification efficiency is closest to:

1. 78 percent
2. 100 percent
3. 110 percent
4. 90 percent

3 · PCR and quantitative PCR · hard

A qPCR standard curve follows Ct = -3.3 x log10(copies) + 38. A sample gives Ct 25. How many target copies were in the reaction?

1. About 87,000 copies
2. About 870 copies
3. About 8,700 copies
4. About 3.9 copies

4 · Molecular diagnostics · medium

A dog treated with doxycycline for 2 weeks has a blood PCR still positive for Ehrlichia canis, but it is now clinically normal. The best interpretation is that PCR:

1. Proves that doxycycline treatment has failed and that this Ehrlichia strain is now resistant to tetracyclines
2. Is always falsely positive after doxycycline
3. Detects nucleic acid and cannot alone distinguish live organisms from residual DNA or a carrier state
4. Shows the dog is now immune

5 · Animal tissue culture · hard

A vaccine manufacturer finds bovine viral diarrhoea virus RNA in a batch made in bovine cells, though no cytopathic effect was seen. The most probable source is:

1. Contamination from the operator's skin
2. Contaminated fetal bovine serum used in the medium
3. Mutation of the vaccine virus into a pestivirus
4. Trypsin of porcine origin

6 · Stem cells · medium

In horses, the most established clinical use of autologous mesenchymal stromal cells has been in:

1. Strangles
2. Laminitis caused by carbohydrate overload as a first-line treatment
3. Superficial digital flexor tendon injuries
4. Equine infectious anaemia

7 · Stem cells · hard

Current evidence suggests that much of the therapeutic effect of injected mesenchymal stromal cells comes from:

1. Secreted paracrine and immunomodulatory factors rather than long-term engraftment
2. Permanent differentiation of the injected cells into all of the injured tissue types they reach
3. Fusion with host neurons
4. Direct killing of bacteria by phagocytosis

8 · Embryo transfer and in-vitro fertilisation · hard

Why do properly washed, zona-intact in-vivo-derived bovine embryos carry a low risk of transmitting many infectious diseases?

1. Embryos generally cannot be infected by any pathogen
2. The intact zona pellucida plus IETS washing (with trypsin for some agents) removes or excludes most pathogens
3. Recipients are always immune to all pathogens
4. Embryos are routinely treated with broad-spectrum antiviral drugs (and antibiotics) before transfer to recipients

9 · Hybridoma technology and monoclonal antibodies · hard

A licensed monoclonal antibody for dogs with osteoarthritis pain works by neutralising:

1. Cyclo-oxygenase-2 enzyme
2. Nerve growth factor
3. Tumour necrosis factor-alpha
4. Interleukin-31 (itch cytokine)

10 · Transgenic animals · hard

Genome-edited polled dairy cattle were later found by a regulatory analysis to carry unintended bacterial plasmid DNA at the edited site. The main lesson for regulators and developers is that:

1. Editing can never introduce foreign DNA, so the plasmid must have come from contamination during sequencing
2. All edited animals must be cloned
3. Polledness is a harmful trait
4. Edited animals need genome-wide or long-read checks for unintended insertions at the target site