Which enzyme is responsible for synthesizing new DNA strands during PCR?
Answer: A
Taq DNA polymerase from Thermus aquaticus is heat-stable and essential for DNA synthesis in PCR cycles.
Q.2Medium
The optimal annealing temperature in PCR is typically set based on:
Answer: C
Annealing temperature is determined by the Tm of primers, calculated using GC content and primer length formulas.
Q.3Easy
In PCR, the denaturation step typically occurs at:
Answer: B
Denaturation separates double-stranded DNA into single strands, requiring high temperatures of 94-95°C.
Q.4Medium
Which of the following is a limitation of conventional PCR?
Answer: C
Conventional PCR detects products only at the end. Real-time PCR (qPCR) monitors amplification during each cycle.
Q.5Medium
What is the primary advantage of real-time PCR (qPCR) over conventional PCR?
Answer: C
qPCR uses fluorescent dyes to monitor product accumulation in real-time, providing quantitative data.
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Q.6Easy
Restriction enzymes recognize and cut DNA at:
Answer: B
Restriction endonucleases recognize specific palindromic DNA sequences and cut predictably at these sites.
Q.7Medium
Which type of restriction enzyme produces 'sticky ends'?
Answer: A
BamHI produces staggered cuts creating complementary single-stranded overhangs (sticky ends). Others like PvuII produce blunt ends.
Q.8Easy
The role of DNA ligase in genetic engineering is to:
Answer: B
DNA ligase catalyzes the formation of phosphodiester bonds between adjacent nucleotides, joining DNA fragments.
Q.9Medium
In RAPD-PCR, the primers are:
Answer: B
RAPD (Random Amplified Polymorphic DNA) uses short, arbitrary primers that amplify random DNA regions, useful for molecular markers.
Q.10Medium
Which technique is most suitable for detecting SNPs (Single Nucleotide Polymorphisms)?
Answer: B
RFLP (Restriction Fragment Length Polymorphism) can detect SNPs that create or eliminate restriction sites.
Q.11Easy
The polymerase chain reaction was invented by:
Answer: B
Kary Mullis invented PCR in 1983, a revolutionary technique that earned him the Nobel Prize in Chemistry in 1993.
Q.12Medium
In DNA fingerprinting, which polymorphic markers are most commonly used in India?
Answer: B
Modern DNA fingerprinting in India uses STRs and SNPs for high discrimination power in forensics and paternity testing.
Q.13Easy
The extension step in PCR occurs at approximately:
Answer: B
Extension/elongation happens at 72-75°C, the optimal temperature for Taq polymerase to synthesize DNA.
Q.14Medium
Which of the following is a common application of PCR in diagnostic medicine?
Answer: A
RT-PCR (Reverse Transcription PCR) is widely used in India and globally for COVID-19 diagnosis by detecting viral RNA.
Q.15Medium
What is the significance of dNTPs in PCR?
Answer: B
dNTPs (dATP, dGTP, dCTP, dTTP) serve as substrates for DNA polymerase to synthesize new DNA strands.
Q.16Hard
In cloning, which vector is most suitable for inserting large DNA fragments (>15 kb)?
Answer: B
Cosmids can accommodate DNA inserts of 35-45 kb, making them ideal for large DNA fragments compared to plasmids (5-20 kb).
Q.17Hard
The principle of AFLP (Amplified Fragment Length Polymorphism) combines:
Answer: A
AFLP integrates restriction enzyme digestion with selective PCR amplification of restriction fragments for genetic diversity analysis.
Q.18Hard
In gene editing, CRISPR-Cas9 uses which type of guide molecule?
Answer: B
CRISPR-Cas9 employs a single guide RNA (sgRNA) that directs Cas9 endonuclease to specific DNA target sequences for precise editing.
Q.19Easy
In PCR, which enzyme synthesizes the complementary DNA strand during the extension phase?
Answer: A
Taq polymerase (thermostable DNA polymerase from Thermus aquaticus) synthesizes new DNA strands at 72°C during the extension phase of PCR.
Q.20Easy
What is the typical number of PCR cycles required to achieve exponential amplification of target DNA?
Answer: B
Standard PCR typically uses 25-35 cycles to achieve sufficient exponential amplification (2^n copies) without compromising specificity or introducing errors.
