dNTPs (deoxynucleotide triphosphates) are the precursor molecules that DNA polymerase incorporates into the growing DNA strand during the extension phase of PCR.
Q.162Medium
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.163Medium
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.
Q.164Medium
In reverse transcription PCR (RT-PCR), which enzyme is critical for the first step?
Answer: B
Reverse transcriptase synthesizes complementary DNA (cDNA) from an RNA template in the first step of RT-PCR, enabling amplification of RNA targets like mRNA.
Q.165Medium
What is the primary advantage of digital PCR (dPCR) over conventional qPCR?
Answer: B
dPCR partitions the PCR reaction into numerous isolated compartments, allowing absolute quantification without requiring a standard curve, and provides higher precision than qPCR.
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Q.166Medium
AFLP (Amplified Fragment Length Polymorphism) technology combines which two DNA techniques?
Answer: B
AFLP combines restriction enzyme digestion with PCR amplification of specific DNA fragments, generating polymorphic banding patterns useful for genetic mapping and strain differentiation.
Q.167Medium
In forensic applications, why are microsatellites (STRs) preferred over SNPs for individual identification?
Answer: B
STRs (Short Tandem Repeats) exhibit high variability between individuals due to differences in repeat numbers, making them ideal for forensic DNA profiling and paternity testing.
Q.168Hard
What is the primary principle of High-Resolution Melting (HRM) analysis in qPCR?
Answer: A
HRM analysis detects genetic variations by monitoring the melting temperature (Tm) of PCR products; sequence variations cause different Tm values, visible as distinct melting curves.
Q.169Hard
In competitive PCR, what is the role of the internal control DNA?
Answer: B
Competitive PCR uses an internal control (competitor) DNA that is amplified simultaneously with the target using the same primers, allowing relative quantification by comparing product amounts.
Q.170Hard
Which PCR variant is most suitable for detecting point mutations in genomic DNA?
Answer: B
ARMS-PCR uses allele-specific primers that only amplify when the primer sequence perfectly matches the target DNA, making it ideal for detecting specific point mutations.
Q.171Hard
In the context of DNA barcoding for species identification, which gene region is commonly used for plants?
Answer: B
For plant DNA barcoding, rbcL (ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit) and matK (maturase K) are the standard barcode regions recognized by CBOL.
Q.172Medium
What is the primary limitation of PCR when amplifying GC-rich sequences?
Answer: B
GC-rich sequences tend to form stable secondary structures (hairpins, loops), which can inhibit primer annealing and polymerase extension, reducing PCR efficiency.
Q.173Hard
In SNP genotyping using TaqMan chemistry, what is the function of MGB (Minor Groove Binder)?
Answer: B
MGB sequences bind in the minor groove of DNA, stabilizing the probe-DNA duplex and increasing its melting temperature, allowing for shorter, more specific probes.
Q.174Hard
Which DNA amplification technique is used to amplify sequences adjacent to a known sequence boundary?
Answer: B
Inverse PCR amplifies unknown DNA sequences flanking a known region by using outward-facing primers on a circularized DNA template, useful for genome walking and transposon mapping.
Q.175Medium
In the diagnosis of genetic disorders, why is allele-specific PCR (AS-PCR) preferred for detecting known mutations?
Answer: B
AS-PCR uses primers with mismatches at the 3' end that only allow amplification when perfectly matched to the target allele, providing rapid and cost-effective mutation detection.
Q.176Medium
What is the primary advantage of using nested PCR in pathogen detection?
Answer: B
Nested PCR uses outer primers for the first amplification round and inner primers for the second round, significantly improving specificity and sensitivity for detecting low-copy pathogens.
Q.177Medium
In whole genome amplification (WGA) using multiple displacement amplification (MDA), which enzyme is used?
Answer: B
Phi29 polymerase, from bacteriophage Phi29, has high processivity and 3' to 5' exonuclease activity, making it ideal for isothermal multiple displacement amplification of entire genomes.
Q.178Easy
Which enzyme is primarily responsible for extending DNA strands during the elongation phase of PCR?
Answer: A
Taq polymerase, derived from Thermus aquaticus, is a heat-stable DNA polymerase that extends primers during PCR elongation at 72°C.
Q.179Easy
In a standard PCR cycle, at what temperature is the DNA double helix typically denatured?
Answer: C
Denaturation occurs at 94-95°C where hydrogen bonds between complementary DNA strands break, separating double-stranded DNA into single strands.
Q.180Medium
Which of the following statements about primer design for PCR is INCORRECT?
Answer: C
High self-complementarity and primer-dimer formation should be avoided as they reduce PCR efficiency and specificity. Primers should have minimal secondary structure.
