Which PCR variant would be most suitable for amplifying DNA from degraded or partially degraded samples such as archaeological or forensic specimens?
Answer: C
Degraded DNA has broken fragments; amplifying short segments (<200 bp) increases success rate compared to long-range PCR which requires intact template.
Q.42Medium
In AFLP (Amplified Fragment Length Polymorphism) analysis, what are the two restriction enzymes typically used?
Answer: B
AFLP uses a rare cutter (EcoRI) and frequent cutter (MseI) to generate polymorphic fragments that are amplified using selective PCR.
Q.43Medium
What is the primary disadvantage of using conventional PCR for pathogen detection in clinical diagnostics compared to real-time PCR?
Answer: B
Conventional PCR provides only end-point detection via gel electrophoresis, lacking real-time kinetic data. qPCR enables quantification during amplification and reduces post-PCR work.
Q.44Medium
In the context of human disease diagnosis, what does the Ct value (Cycle threshold) in qPCR represent?
Answer: B
Ct is the cycle at which fluorescence surpasses background, inversely correlating with initial template amount. Lower Ct = higher initial DNA quantity.
Q.45Medium
Which DNA fingerprinting technique using PCR amplification of repetitive sequences is widely used in paternity testing and criminal investigations in India?
Answer: B
STR profiling amplifies variable number tandem repeats (VNTRs) and is the gold standard for DNA fingerprinting in forensics, recognized by Indian law enforcement and courts.
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Q.46Medium
In homozygous versus heterozygous allele detection using allele-specific PCR, which outcome indicates a heterozygous genotype?
Answer: A
Heterozygotes carry both alleles; separate allele-specific primer sets each amplify their respective allele, showing amplification in both reactions.
Q.47Medium
In the context of environmental microbiology, what does PCR-DGGE (Denaturing Gradient Gel Electrophoresis) primarily assess?
Answer: B
PCR-DGGE separates PCR amplicons based on melting behavior, providing a fingerprint of microbial community structure independent of culture.
Q.48Medium
In next-generation sequencing library preparation, why is PCR amplification of adaptor-ligated DNA fragments critical?
Answer: C
NGS requires substantial DNA; PCR amplifies adaptor-ligated fragments while incorporating index sequences for multiplexing, enabling efficient library preparation.
Q.49Medium
During PCR amplification, the annealing temperature is set based on the Tm (melting temperature) of primers. If primers with Tm of 58°C and 62°C are used in the same reaction, what would be the optimal annealing temperature to ensure efficient amplification of both targets?
Answer: B
The optimal annealing temperature should be set at or slightly below the Tm of the primer with the lowest Tm (58°C) to prevent primer dissociation while maintaining specificity. Using 58°C ensures both primers can bind efficiently.
Q.50Medium
In a multiplex PCR assay designed to simultaneously amplify 6 different STR (short tandem repeat) loci for forensic DNA profiling, what is the critical consideration that must be addressed?
Answer: A
In multiplex PCR, primers with similar Tm values ensure equal amplification efficiency across all targets. Amplicons of comparable sizes prevent preferential amplification of shorter fragments (which amplify faster), ensuring balanced and accurate STR profiles for individual identification.
