Genetics and molecular biology basics relevant to medicinal plants MCQs With Answer

Introduction: This quiz collection focuses on genetics and molecular biology fundamentals essential for understanding and manipulating medicinal plants. Designed for M.Pharm students taking Medicinal Plant Biotechnology (MPG 201T), it covers DNA replication, gene expression, molecular markers, transformation tools, gene regulation, genome editing, and analytical methods used to study biosynthetic pathways of therapeutically important metabolites. Questions emphasize practical concepts such as PCR, blotting techniques, marker-assisted selection, epigenetics, and strategies to optimize transgene expression in plants. These MCQs aim to deepen conceptual clarity and prepare you for research or applied work in medicinal plant genetic improvement and molecular analysis.

Q1. Which phase of the plant cell cycle is directly associated with genomic DNA replication?

• G1 phase
• S phase
• G2 phase
• M phase

Correct Answer: S phase

Q2. Which component is essential for DNA amplification in conventional PCR because it tolerates high denaturation temperatures?

• Reverse transcriptase
• Thermostable DNA polymerase
• DNA ligase
• Single-stranded DNA binding protein

Correct Answer: Thermostable DNA polymerase

Q3. Real-time quantitative PCR (qPCR) measures nucleic acid quantity by which primary mechanism?

• Detecting radio-labeled nucleotides incorporated into products
• Visualizing bands after gel electrophoresis at end-point
• Monitoring fluorescence emitted during each PCR cycle
• Measuring the decrease of template DNA concentration

Correct Answer: Monitoring fluorescence emitted during each PCR cycle

Q4. Which molecular technique is specifically used to detect presence and size of particular DNA fragments after restriction digestion?

• Northern blotting
• Western blotting
• Southern blotting
• Eastern blotting

Correct Answer: Southern blotting

Q5. To analyze steady-state mRNA levels of a biosynthetic enzyme in a medicinal plant, which method is most appropriate?

• Northern blotting
• Southern blotting
• Restriction fragment length polymorphism (RFLP)
• Immunoblotting (Western blot)

Correct Answer: Northern blotting

Q6. Agrobacterium tumefaciens is widely used in plant transformation because it naturally mediates what process?

• Integration of T-DNA into the plant nuclear genome
• Replication of circular plasmids in chloroplasts
• Horizontal transfer of mitochondrial DNA
• Packaging of viral vectors for infection

Correct Answer: Integration of T-DNA into the plant nuclear genome

Q7. What is a key advantage of plastid (chloroplast) transformation for producing recombinant proteins in plants?

• Transgenes are transmitted via pollen at very high frequency
• Low gene copy number reduces expression variability
• High gene copy number and maternal inheritance reduce transgene escape
• Improved nuclear splicing of transgene transcripts

Correct Answer: High gene copy number and maternal inheritance reduce transgene escape

Q8. RNA interference (RNAi) silences gene expression by which mechanism?

• Ribosomal stalling at the start codon
• Dicer processing of dsRNA into siRNAs that guide RISC to degrade target mRNA
• Methylation of promoter DNA to block transcription
• Insertion of transposons into coding regions

Correct Answer: Dicer processing of dsRNA into siRNAs that guide RISC to degrade target mRNA

Q9. Successful CRISPR-Cas9 cleavage at a genomic target requires which short adjacent motif?

• Start codon (AUG)
• PAM (protospacer adjacent motif)
• Polyadenylation signal (AAUAAA)
• TATA box

Correct Answer: PAM (protospacer adjacent motif)

Q10. Which molecular marker type is characterized by tandem repeat motifs and is co-dominant, making it useful for assessing heterozygosity?

• RAPD (Random Amplified Polymorphic DNA)
• SSR (Simple Sequence Repeat / microsatellite)
• AFLP (Amplified Fragment Length Polymorphism)
• RFLP (Restriction Fragment Length Polymorphism)

Correct Answer: SSR (Simple Sequence Repeat / microsatellite)

Q11. Which statement correctly distinguishes SNPs from microsatellites (SSRs)?

• SNPs are multi-allelic and highly variable in repeat number
• SSRs are typically bi-allelic and single nucleotide changes
• SNPs are single nucleotide polymorphisms and are usually bi-allelic
• SSRs detect single nucleotide changes across genomes

Correct Answer: SNPs are single nucleotide polymorphisms and are usually bi-allelic

Q12. Quantitative trait locus (QTL) mapping in medicinal plants is used to:

• Identify exact nucleotide changes responsible for a trait without linkage analysis
• Map genomic regions associated with variation in quantitative traits such as metabolite content
• Produce transgenic plants by direct gene insertion
• Quantify transcript abundance by hybridization

Correct Answer: Map genomic regions associated with variation in quantitative traits such as metabolite content

Q13. Which promoter is commonly used to drive strong constitutive expression of transgenes in many plant species?

• lac promoter
• SV40 promoter
• CaMV 35S promoter
• T7 promoter

Correct Answer: CaMV 35S promoter

Q14. Codon optimization of a transgene for expression in plants primarily aims to:

• Introduce introns to increase mRNA stability
• Match host tRNA abundance to improve translational efficiency
• Change amino acid sequence to increase enzyme activity
• Create novel splice variants for regulation

Correct Answer: Match host tRNA abundance to improve translational efficiency

Q15. In qPCR experiments comparing transcript levels between samples, normalization is performed by:

• Using a stably expressed reference (housekeeping) gene to correct for input and RT efficiency
• Comparing raw Ct values without any controls
• Running PCR for fewer cycles to avoid amplification
• Relying solely on end-point gel band intensity

Correct Answer: Using a stably expressed reference (housekeeping) gene to correct for input and RT efficiency

Q16. Which epigenetic modification in plants is most directly associated with long-term transcriptional repression of genes?

• Acetylation of histone tails
• DNA methylation of cytosines
• Phosphorylation of RNA polymerase II
• Ubiquitination of membrane proteins

Correct Answer: DNA methylation of cytosines

Q17. Transcription factors from which family commonly regulate phenylpropanoid and flavonoid biosynthesis in plants?

• MYB family
• Homeobox (HOX) family only
• Heat shock factor (HSF) family exclusively
• Ribosomal protein family

Correct Answer: MYB family

Q18. A selectable marker frequently used in plant transformation confers resistance to which antibiotic via the nptII gene?

• Penicillin
• Kanamycin
• Chloramphenicol
• Tetracycline

Correct Answer: Kanamycin

Q19. In most angiosperm species, organelle genomes (chloroplast and mitochondrial) are predominantly inherited through which route?

• Paternal inheritance via pollen
• Maternal inheritance via the egg cytoplasm
• Biparental inheritance equally from both parents
• De novo synthesis in each generation

Correct Answer: Maternal inheritance via the egg cytoplasm

Q20. Which strategy reduces off-target mutations when using CRISPR-Cas9 in plant genome editing?

• Using wild-type Cas9 at very high concentrations
• Employing high-fidelity Cas9 variants or paired nickases
• Designing guide RNAs with many mismatches to increase tolerance
• Avoiding PAM sequences near the target

Correct Answer: Employing high-fidelity Cas9 variants or paired nickases

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