Which PCR variant is specifically designed for amplifying and detecting microRNA (miRNA) targets in clinical samples?
Answer: B
Stem-loop RT-PCR uses a stem-loop primer structure that specifically binds to mature miRNAs, making it ideal for miRNA detection and quantification in diagnostic applications.
Q.42Medium
In RAPD-PCR (Random Amplified Polymorphic DNA), what is the primary application in agricultural biotechnology?
Answer: A
RAPD-PCR uses random primers to generate DNA fingerprints for assessing genetic diversity, distinguishing crop varieties, and parentage analysis in breeding programs.
Q.43Medium
During DNA amplification using PCR, if the initial template has 2 copies, approximately how many copies will be present after 30 cycles (assuming 100% efficiency)?
Answer: C
PCR follows exponential amplification: Final copies = Initial copies × 2ⁿ, where n = number of cycles. 2 × 2³⁰ = 2 × 1.07 × 10⁹ ≈ 2 × 10⁹ copies.
Q.44Medium
What is the main disadvantage of using standard Taq polymerase compared to high-fidelity polymerases like Pfu in PCR?
Answer: B
Taq polymerase lacks 3' to 5' exonuclease (proofreading) activity, resulting in ~1 error per 10,000 bases. Pfu has proofreading activity, reducing errors to ~1 per 10 million bases.
Q.45Medium
In multiplex PCR, what is the critical challenge that must be addressed when designing multiple primer sets?
Answer: B
Multiplex PCR requires careful primer design to prevent primer-primer interactions, dimer formation, and ensure specific amplification of all target sequences simultaneously.
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Q.46Medium
Which DNA technology technique combines random DNA fragmentation with sequence-independent single-primer amplification (SISPA)?
Answer: B
WGA using SISPA allows amplification of entire genomes from minimal starting material by using random primers and is useful for viral and microbial genomics.
Q.47Medium
In droplet digital PCR (ddPCR), how does partitioning of the sample improve quantification accuracy compared to conventional qPCR?
Answer: B
ddPCR partitions the sample into thousands of water-in-oil emulsion droplets, allowing independent amplification and enabling absolute quantification without standard curves.
Q.48Medium
For amplifying extremely long DNA fragments (>10 kb), which specialized PCR technique is most appropriate?
Answer: B
Long-range PCR uses high-fidelity polymerases (like Pfu or Phusion), extended extension times, and optimized Mg²⁺ concentrations to amplify fragments >10 kb.
Q.49Medium
In CRISPR-Cas9 gene editing, what is the function of the PAM (Protospacer Adjacent Motif) sequence?
Answer: B
The PAM sequence (typically NGG for Streptococcus pyogenes Cas9) is recognized by the Cas9-gRNA complex to identify and cleave target DNA at specific locations.
Q.50Hard
Which DNA technology is most suitable for detecting chromosomal abnormalities like deletions and duplications at the genomic level?
Answer: A
Array-CGH (aCGH) provides high-resolution detection of chromosomal imbalances across the entire genome, making it ideal for identifying deletions and duplications.
Q.51Medium
In next-generation sequencing (NGS) library preparation, what is the primary purpose of adapter ligation in DNA technology workflows?
Answer: B
Adapters are short synthetic DNA sequences ligated to fragmented DNA ends, enabling cluster generation, primer binding, and sequencing on NGS platforms.
Q.52Hard
When designing a TaqMan probe for qPCR, what is the relationship between probe length and specificity in target detection?
Answer: B
TaqMan probes of 18-25 bp with Tm 5-10°C higher than primers provide optimal specificity and sensitivity by requiring perfect base pairing for nuclease cleavage.
Q.53Hard
In forensic DNA analysis using STR markers, what advantage do newer SNP-based methods provide over traditional STR typing for 2024-25 investigations?
Answer: B
SNP-based methods offer lower mutation rates (~10⁻⁸), enable ancestry inference, and work better with degraded DNA samples compared to STRs, making them valuable for cold cases.
Q.54Hard
Which PCR-based technique is specifically used to amplify and sequence unknown DNA flanking regions of known sequences?
Answer: B
Inverse PCR uses outward-facing primers on a circularized DNA template to amplify and sequence flanking regions of known sequences, useful for finding regulatory elements.
Q.55Hard
In GWAS (Genome-Wide Association Studies) using DNA microarrays, what statistical principle is applied to identify significant SNP-trait associations?
Answer: A
GWAS uses Chi-square tests with Bonferroni correction (or FDR correction) to account for multiple hypothesis testing across millions of SNPs and identify genome-wide significant associations.
Q.56Easy
What is the primary principle behind whole exome sequencing (WES) in identifying disease-causing mutations?
Answer: A
WES captures and sequences exonic regions (~50 Mb) using targeted enrichment, reducing sequencing depth and cost while identifying 85-90% of disease-causing variants.
Q.57Medium
In the context of DNA barcode libraries for species identification in 2024-25, which universal marker is most commonly used for plants?
Answer: B
rbcL (ribulose-1,5-bisphosphate carboxylase) and matK are standard DNA barcodes for plant identification due to appropriate evolutionary rates and amplification efficiency.
Q.58Easy
What is the optimal annealing temperature range for most PCR reactions?
Answer: A
The annealing temperature typically ranges from 45-65°C and depends on the Tm (melting temperature) of the primers used. This temperature allows primers to bind specifically to target DNA.
Q.59Easy
Which thermostable DNA polymerase is most commonly used in standard PCR?
Answer: A
Taq polymerase, isolated from Thermus aquaticus, is the most widely used enzyme in PCR due to its heat stability and ability to synthesize DNA at high temperatures.
Q.60Easy
In a typical PCR cycle, DNA denaturation occurs at approximately which temperature?
Answer: B
DNA denaturation in PCR occurs at 94-95°C (or sometimes 98°C), where hydrogen bonds between DNA strands are broken, separating the double helix into single strands.
