UPHESC Assistant Professor Genetics & Plant Breeding PYQs

Concept: Mariani et al. (1990, 1992) expressed the barnase (RNase from Bacillus amyloliquefaciens) gene under the tapetum-specific TA29 promoter in tobacco and oilseed rape; the barstar inhibitor gene restores fertility in F₁.

1. The system (Plant Genetic Systems, Belgium) is used commercially in canola/rapeseed hybrids; in India, GM mustard DMH-11 uses barnase–barstar.
2. Cotton, maize and bajra hybrids mainly use CMS or GMS.

Short trick: Barnase kills tapetum, Barstar rescues – tobacco & Brassica.

Concept: Reverse breeding (Dirks et al., 2009) suppresses meiotic crossing over in an elite heterozygous plant, recovers non-recombinant spores as doubled haploids, and selects complementary pairs that, when crossed, recreate the original hybrid – i.e. the parental lines are regenerated.

1. Polycross – testing GCA of clones.
2. Shuttle breeding – two generations a year at contrasting sites (Borlaug).
3. Inbreeding – selfing to homozygosity, not reconstruction of parents.

Short trick: Reverse breeding: hybrid → its parents.

Concept: Average degree of dominance $\sqrt{H_1/D}$ > 1 indicates overdominance.

1. 0 → no dominance; 0–1 → partial; = 1 → complete; > 1 → over-dominance.
2. (Here the printed ratio means $\sqrt{H_1/D}$.)

Short trick: > 1 = Over.

Concept: H. G. Khorana's group (1970) made the 77-bp yeast alanine-tRNA gene – the first artificial gene – by chemically synthesising short oligonucleotides by the phosphodiester method and then joining them with DNA ligase.

1. Phosphotriester method came in the 1970s (Letsinger, Reese); phosphite-triester/phosphoramidite (Caruthers, 1981) is used in modern automated synthesisers.
2. Ligation was only the joining step; the approach is known as the phosphodiester approach.

Short trick: Khorana 1970 → phosphodiester; Caruthers 1981 → phosphoramidite.

Concept: M13 is a filamentous single-stranded DNA phage; its vectors (M13mp series, Messing) give single-stranded template DNA directly – ideal for Sanger dideoxy sequencing.

1. λ and cosmid vectors – for large inserts/genomic libraries.
2. Plasmids need denaturation to give template.

Short trick: Single-stranded M13 = sequencing template.

Concept: Escherichia coli (strains like K-12 derivatives DH5α, JM109) is the most widely used cloning host: fast growth, simple genetics, easy transformation and many compatible vectors.

1. Bacillus subtilis and yeast are used for secretion/eukaryotic expression but less commonly.

Short trick: Cloning workhorse = E. coli.

Concept: Microsatellites are tandem repeats of 1–6 bp motifs; PCR with flanking primers gives Simple Sequence Repeat (SSR) markers – co-dominant and highly polymorphic.

1. CAPS – PCR + restriction digestion.
2. RAPD – random 10-mer primers, dominant.
3. RFLP – restriction + Southern hybridisation.

Short trick: Microsatellite = SSR = STR.

Concept: Chromosome walking moves from a known marker to a target gene through overlapping genomic clones; large-insert libraries (cosmid ~35–45 kb, later BAC/YAC) are used so that each 'step' covers a long stretch.

1. An end fragment of one clone is used as probe to pick the next overlapping clone, and so on.
2. Cosmid libraries were the classical choice because inserts are much larger than in plasmid or λ libraries.

Short trick: Long steps need long inserts → cosmid (BAC/YAC).

Concept: Flavr Savr (Calgene, USA, 1994) – the first commercial GM food – carried an antisense copy of the polygalacturonase (PG) gene, which blocked PG synthesis and delayed fruit softening.

1. Antisense RNA pairs with PG mRNA and prevents its translation.
2. Barnase–barstar is for male sterility; ribozymes cleave RNA catalytically.

Short trick: Flavr Savr = antisense PG.

Concept: Genomic selection (Meuwissen, Hayes and Goddard, 2001) uses genome-wide dense markers (SNPs) simultaneously to predict genomic estimated breeding values (GEBVs) of candidates.

1. A training population (genotyped + phenotyped) builds the prediction model; the breeding population is then selected on GEBV alone.
2. Unlike MAS, it does not need significant QTL first.

Short trick: Whole-genome markers → GEBV → Genomic selection.

Concept: J. H. Taylor, Woods and Hughes (1957) labelled root-tip chromosomes of Vicia faba with ³H-thymidine and showed by autoradiography that chromosomes replicate semi-conservatively.

1. Meselson & Stahl (1958) – E. coli, ¹⁵N/¹⁴N, CsCl gradient.
2. Cairns (1963) – autoradiography of E. coli chromosome (theta replication).

Short trick: Vicia faba + tritium = Taylor; E. coli + ¹⁵N = Meselson–Stahl.

Concept: R. H. Painter (1951, 'Insect Resistance in Crop Plants') classified the mechanisms of resistance as non-preference, antibiosis and tolerance.

1. Kogan & Ortman (1978) renamed non-preference as antixenosis.
2. Havens (1792) first reported Hessian-fly-resistant wheat, but did not propose mechanisms.

Short trick: Painter's triad: non-preference, antibiosis, tolerance.

Concept: Reproductive meristems (developing inflorescences, ovaries) do not transpire much and are hydraulically buffered, so at a given time their water stress is lower than in actively transpiring leaves.

1. Leaves lose water directly to the atmosphere and show the most negative water potential.
2. Yet reproductive stages are the most sensitive to drought, because even mild stress there disrupts pollen and grain set.

Short trick: Transpiring leaf = most stressed; meristem = buffered (less stress).

Concept: The first commercial multiline wheat was Miramar 63 (followed by Miramar 65), released in Colombia (1960s) from the Rockefeller-supported programme, based on Borlaug's multiline concept for rust resistance.

1. In India the first multiline wheats were KSML 3 (Kalyan Sona based) and MLKS 11 (1979–81).
2. Kalyan Sona and Sonalika are ordinary pure-line dwarf varieties from CIMMYT material.

Short trick: Colombia → Miramar 63; India → KSML 3.

Concept: Salicylic acid is a phenolic signal molecule (hormone) that induces PR proteins in systemic acquired resistance – it is not itself a protein.

1. PR-2 = β-1,3-glucanase; PR-3 (and 4, 8, 11) = chitinases; PR-5 = thaumatin-like proteins.
2. SA → NPR1 → PR gene expression → SAR.

Short trick: SA induces PR proteins; it is not one.

Concept: Heat tolerance is a complex quantitative trait (membrane thermostability, canopy temperature depression, grain filling, pollen viability, HSP expression) controlled by many genes – polygenic, with marked G × E interaction.

1. QTL for heat tolerance are numerous, each with small effect.
2. Hence it is improved by selection under stress, indices and genomic tools rather than single-gene transfer.

Short trick: Abiotic stress tolerance = polygenic.

Concept: In diploid B. campestris (B. rapa, AA genome) erucic acid is controlled by a single gene pair (FAE1 locus) with additive alleles; in amphidiploid B. napus and B. juncea two gene pairs (one in each genome) are involved.

1. Low-erucic (<2%) 'canola' quality needs the recessive (zero-erucic) alleles.
2. Embryo genotype (not maternal plant) determines erucic acid in the seed.

Short trick: Diploid campestris – 1 gene; amphidiploids napus/juncea – 2 genes.

Concept: Abscisic acid (ABA) accumulates under drought, salinity and cold; it closes stomata and induces stress-protective genes – hence the 'stress hormone'.

1. It also promotes dormancy and abscission; auxin, GA and cytokinin are growth promoters.

Short trick: ABA = stress & stomatal closure.

Concept: The National Seeds Project (Phase I) was launched in 1975 with World Bank assistance to build state seed corporations, seed processing plants and certification agencies.

1. Phase II – 1978; Phase III – 1990.
2. Related milestones: NSC 1963; Seeds Act 1966; Seed Review Team 1968; Seed Policy 1988.

Short trick: NSC 1963 → Seeds Act 1966 → NSP 1975.

Concept: The Patent Office has its head office at Kolkata, with branch offices at Delhi, Mumbai and Chennai; it works under the Controller General of Patents, Designs & Trade Marks (CGPDTM), whose office is in Mumbai.

1. GI Registry – Chennai; Trade Marks Registry head office – Mumbai; Copyright Office – New Delhi.

Short trick: Patent – Kolkata; GI – Chennai; TM – Mumbai.