Which annealing temperature is most appropriate for primers with a GC content of 50%?
Answer: B
Annealing temperature is typically 3-5°C below the Tm (melting temperature). For 50% GC content, Tm ≈ 55-60°C, making this the appropriate annealing range.
Q.62Medium
In next-generation sequencing (NGS), what is the primary advantage of massively parallel sequencing over conventional Sanger sequencing?
Answer: A
NGS provides massively parallel sequencing, generating millions of reads simultaneously, offering significantly lower cost per base and much higher throughput compared to Sanger sequencing.
Q.63Medium
What is the purpose of using a 'hot start' Taq polymerase in PCR?
Answer: B
Hot start Taq polymerase is inactive at room temperature and becomes activated only at high temperatures (95°C), preventing unwanted non-specific amplification during setup.
Q.64Medium
In DNA barcoding for species identification, which gene region is most commonly used?
Answer: B
COI (cytochrome c oxidase I) is the standard DNA barcode for animal identification due to its high interspecific variation and low intraspecific variation.
Q.65Medium
Which of the following best describes the principle of digital PCR (dPCR)?
Answer: B
Digital PCR partitions the sample into thousands of individual reactions (droplets), allowing absolute quantification by counting positive and negative partitions without requiring standard curves.
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Q.66Medium
In gene therapy, AAV (Adeno-associated virus) vectors are preferred because they:
Answer: B
AAVs are preferred due to minimal immunogenic response, ability to target specific tissues, and safe integration properties, despite a packaging limit of ~4.7 kb.
Q.67Medium
What is the principle behind site-directed mutagenesis using PCR?
Answer: B
Site-directed mutagenesis uses primers with mismatches at the desired mutation site. During PCR extension, the mutated sequence is copied, incorporating the specific change.
Q.68Medium
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.69Medium
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.70Medium
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.71Medium
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.72Medium
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.
Q.73Medium
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.74Medium
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.75Medium
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.76Medium
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.77Medium
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.78Medium
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.79Medium
Real-time PCR (qPCR) differs from conventional PCR in that it:
Answer: B
qPCR continuously monitors the accumulation of PCR products in real-time using fluorescent reporters (SYBR Green or TaqMan probes), allowing quantification of the target DNA.
Q.80Medium
Which of the following is a common application of multiplex PCR?
Answer: A
Multiplex PCR amplifies multiple target sequences in a single reaction tube using multiple primer pairs, enabling detection of several genetic markers, genes, or pathogens simultaneously.
