ASRB NET and ARS / SMS / STO (Agricultural Scientists Recruitment Board) · India · Agricultural Scientists Recruitment Board
Original practice questions written to the published syllabus · not past papersMolecular tools used in diagnosis, vaccines and reproduction: recombinant DNA, PCR, cell culture, monoclonal antibodies, cloning, transgenics and genomics, with their biosafety rules.
In the exams: ICAR AICE-JRF core group 08; ICAR AIEEA-PG 12 (Animal Biotechnology)
How our questions for ASRB NET and ARS / SMS / STO spread across the units of Veterinary and Animal Biotechnology. Difficulty: 28 easy, 59 medium, 32 hard.
| Genomics and bioinformatics | 15 | |
| PCR and quantitative PCR | 13 | |
| Embryo transfer and in-vitro fertilisation | 13 | |
| Molecular biology and recombinant DNA | 11 | |
| Molecular diagnostics | 9 | |
| Animal tissue culture | 9 | |
| Sub-unit and recombinant vaccines | 9 | |
| Hybridoma technology and monoclonal antibodies | 8 | |
| Stem cells | 8 | |
| Cloning | 8 | |
| Transgenic animals | 8 | |
| Biosafety and regulation | 8 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
Bovine leukocyte adhesion deficiency (BLAD) in Holstein cattle is caused by a mutation in the gene for:
B. The integrin beta-2 subunit (CD18)
BLAD is an autosomal recessive defect in CD18 (ITGB2), so neutrophils cannot adhere and migrate, and calves have recurrent infections. Uridine monophosphate synthase is DUMPS, the ryanodine receptor is porcine stress syndrome, myostatin is double muscling.
You need 10 mL of medium seeded at 2 x 10^5 cells per mL from a suspension containing 1 x 10^6 cells per mL. What volume of suspension do you add?
D. 2 mL, made up to 10 mL with medium
C1V1 = C2V2: V1 = (2 x 10^5 x 10)/(1 x 10^6) = 2 mL. 5 mL mistakes the dilution factor (10^6 / 2 x 10^5) for a volume, and a decimal slip gives 0.2 mL; 20 mL slips an exponent, reading the stock as 1 x 10^5 cells per mL.
In hybridoma production, the myeloma fusion partner is chosen to lack which enzyme so that unfused myeloma cells die in HAT medium?
D. Hypoxanthine-guanine phosphoribosyltransferase (HGPRT)
Aminopterin in HAT blocks dihydrofolate reductase and thus de novo nucleotide synthesis. Cells must use the salvage pathway, which needs HGPRT. HGPRT-negative myeloma cells die; hybrids gain HGPRT from the spleen B cell. Dihydrofolate reductase is the enzyme aminopterin blocks, not the one missing from the myeloma.
Further reading: Kohler G, Milstein C. Nature 1975;256:495-497.
Unfused spleen B cells do not survive long after a hybridoma fusion because:
B. Normal B cells have a limited lifespan in culture
Primary B cells have HGPRT, so HAT does not kill them, but they cannot divide indefinitely and die within days. Only fused hybrids combine immortality with HGPRT.
After hybridoma fusion, antibody-positive wells are subcloned by limiting dilution. The purpose is to:
D. Ensure the culture derives from a single cell so the antibody is truly monoclonal
An early positive well may contain several hybrid clones. Plating at about one cell per well or less and re-screening ensures a single clone. Class switching does not happen in culture this way.
In horses, the most established clinical use of autologous mesenchymal stromal cells has been in:
C. Superficial digital flexor tendon injuries
Bone-marrow or adipose-derived cells injected into core lesions of the superficial digital flexor tendon are the best-known equine application, though the controlled-trial evidence is still limited. They are not a treatment for viral or bacterial infections.
Dolly the sheep was produced by somatic cell nuclear transfer using a nucleus from which cell type?
C. A mammary gland cell of an adult ewe
Dolly (Roslin Institute, born 1996) came from a mammary epithelial cell of a six-year-old Finn Dorset ewe placed in an enucleated oocyte from a Scottish Blackface ewe. Fetal fibroblasts and embryonic cells were also used as donors in the same study, but Dolly was the adult-cell clone.
Further reading: Wilmut I et al. Nature 1997;385:810-813.
A licensed monoclonal antibody for dogs with osteoarthritis pain works by neutralising:
B. Nerve growth factor
Anti-NGF antibodies (caninised for dogs, felinised for cats) reduce osteoarthritis pain signalling. The anti-IL-31 antibody is for pruritus in atopic dermatitis; COX-2 is inhibited by small-molecule NSAIDs, not antibodies. Availability varies by country.
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:
D. Edited animals need genome-wide or long-read checks for unintended insertions at the target site
Checking only that the intended allele is present missed the integrated plasmid backbone including antibiotic-resistance genes. Thorough sequencing of the edited locus and genome is now expected.
Genomic selection, as proposed by Meuwissen, Hayes and Goddard in 2001, predicts breeding values from:
C. Dense genome-wide marker effects estimated in a reference population
Genomic selection sums the estimated effects of thousands of genome-wide SNPs, capturing many small-effect loci. Using one linked marker is marker-assisted selection; pedigree-only and progeny-test methods are the traditional approaches.
Further reading: Meuwissen THE, Hayes BJ, Goddard ME. Genetics 2001;157:1819-1829.
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