Which annealing temperature is most appropriate for primers with a GC content of 50%?

The correct answer is B: 55-60°C. 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.

A genetically modified organism (GMO) shows unexpected phenotypic changes not related to the introduced transgene. What biological phenomenon best explains this?

The correct answer is C: Position effect and integration-induced mutations. When foreign DNA integrates into the genome, it can disrupt endogenous genes or be influenced by local chromatin context (position effect), causing unintended phenotypic changes beyond the transgene's direct effect.

In a typical PCR cycle, DNA denaturation occurs at approximately which temperature?

The correct answer is B: 94-95°C. 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.

In droplet digital PCR (ddPCR), the sample is partitioned into thousands of micro-compartments. What is the primary advantage of this approach?

The correct answer is B: Enables absolute quantification without standard curves. ddPCR partitions samples into independent reactions, allowing Poisson distribution analysis for absolute quantification without reference standards.

In Bt cotton cultivation in India, the Cry1Ac toxin primarily targets which insect order?

The correct answer is A: Lepidoptera. Cry1Ac toxin from Bacillus thuringiensis specifically targets lepidopteran pests like cotton bollworms. It binds to specific receptors in their midgut.

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Biotechnology
PCR & DNA Technology

Genetic engineering, fermentation, cell biology

28 Q 3 Topics Take Mock Test

Difficulty: All Easy Medium Hard 21–28 of 28

Topics in Biotechnology

All Genetic Engineering 100 PCR & DNA Technology 100 Cell Culture 60

Q.21 Hard PCR & DNA Technology

CRISPR-Cas12 (Cpf1) differs from Cas9 in that it:

A Requires RNA-only guidance

B Creates sticky ends (TALEN-like overhangs) and requires only single RNA molecule

C Is more efficient for prokaryotic editing

D Does not require PAM sequences

Correct Answer: B. Creates sticky ends (TALEN-like overhangs) and requires only single RNA molecule

EXPLANATION

Cas12 creates staggered cuts resulting in sticky ends, requires only one CRISPR RNA (not separate tracrRNA), and recognizes T-rich PAM sequences, offering advantages for some applications.

Test

Q.22 Hard PCR & DNA Technology

What is the significance of the primer Tm (melting temperature) in multiplex PCR?

A All primers should have similar Tm values to allow use of single annealing temperature

B Primers should have different Tm values for better specificity

C Tm has no relevance in multiplex PCR

D Higher Tm always indicates better performance

Correct Answer: A. All primers should have similar Tm values to allow use of single annealing temperature

EXPLANATION

In multiplex PCR, all primers should have similar Tm values (within 1-2°C) to use a single annealing temperature, preventing preferential amplification of certain targets.

Test

Q.23 Hard PCR & DNA Technology

In the context of 2024-25 genomic studies, what is the primary advantage of long-read sequencing technologies (PacBio, Oxford Nanopore) over short-read NGS?

A Higher accuracy

B Lower cost

C Better assembly of repetitive regions and structural variants

D Requires less DNA input

Correct Answer: C. Better assembly of repetitive regions and structural variants

EXPLANATION

Long-read sequencing can span repetitive sequences and detect large structural variations that short-reads cannot resolve, improving genome assembly quality.

Test

Q.24 Hard PCR & DNA Technology

Which technique combines PCR with capillary electrophoresis for high-resolution DNA fragment analysis?

A AFLP

B Microsatellite genotyping

C RFLP

D Southern blotting

Correct Answer: B. Microsatellite genotyping

EXPLANATION

Microsatellite (STR) genotyping uses PCR followed by capillary electrophoresis for precise size determination of amplified fragments for forensic and population studies.

Test

Q.25 Hard PCR & DNA Technology

In forensic DNA analysis, STR (Short Tandem Repeat) profiling is preferred over SNPs because:

A STRs are more conserved across populations

B STRs show higher polymorphism and discrimination power

C SNPs require more PCR cycles

D STRs are less affected by degradation

Correct Answer: B. STRs show higher polymorphism and discrimination power

EXPLANATION

STRs (variable number tandem repeats) show higher allelic variation than SNPs, providing greater discrimination power for individual identification in forensic cases.

Test

Q.26 Hard PCR & DNA Technology

In gene editing, CRISPR-Cas9 uses which type of guide molecule?

A Single-stranded DNA (ssDNA)

B Guide RNA (sgRNA)

C Protein only

D Restriction enzyme

Correct Answer: B. Guide RNA (sgRNA)

EXPLANATION

CRISPR-Cas9 employs a single guide RNA (sgRNA) that directs Cas9 endonuclease to specific DNA target sequences for precise editing.

Test

Q.27 Hard PCR & DNA Technology

The principle of AFLP (Amplified Fragment Length Polymorphism) combines:

A Restriction digestion and PCR amplification

B Southern blotting and sequencing

C RFLP and DNA fingerprinting only

D Gel electrophoresis and RAPD

Correct Answer: A. Restriction digestion and PCR amplification

EXPLANATION

AFLP integrates restriction enzyme digestion with selective PCR amplification of restriction fragments for genetic diversity analysis.

Test

Q.28 Hard PCR & DNA Technology

In cloning, which vector is most suitable for inserting large DNA fragments (>15 kb)?

A Plasmid vectors

B Cosmid vectors

C Phage vectors

D Phagemid vectors

Correct Answer: B. Cosmid vectors

EXPLANATION

Cosmids can accommodate DNA inserts of 35-45 kb, making them ideal for large DNA fragments compared to plasmids (5-20 kb).

Test

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