Which epigenetic modification is commonly exploited in epigenome editing to achieve stable gene silencing without altering DNA sequence?
Answer: B
dCas9-KRAB recruits repressor complexes causing DNA methylation and histone deacetylation, establishing stable heterochromatin without genetic changes, useful for therapeutic gene silencing.
Q.22Hard
What is the primary mechanism of action of TALENs (Transcription Activator-Like Effector Nucleases) in gene editing?
Answer: B
TALENs consist of a modular DNA-binding domain (which recognizes specific sequences) fused to the FokI nuclease domain, allowing precise DNA cleavage at target sites.
Q.23Hard
In next-generation sequencing (NGS), what is the primary advantage of whole-genome sequencing over targeted gene sequencing?
Answer: B
Whole-genome sequencing provides unbiased coverage of the entire genome, allowing discovery of unexpected mutations, copy number variations, and structural rearrangements not detected by targeted approaches.
Q.24Hard
Which of the following represents a limitation of homologous recombination-based gene targeting?
Answer: B
Homologous recombination has very low frequency in mammalian cells compared to yeast, requiring enrichment strategies and selection markers. This limitation has been overcome by CRISPR technology.
Q.25Hard
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).
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Q.26Hard
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.27Hard
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.28Hard
In forensic DNA analysis, STR (Short Tandem Repeat) profiling is preferred over SNPs because:
Answer: B
STRs (variable number tandem repeats) show higher allelic variation than SNPs, providing greater discrimination power for individual identification in forensic cases.
Q.29Hard
Which technique combines PCR with capillary electrophoresis for high-resolution DNA fragment analysis?
Answer: B
Microsatellite (STR) genotyping uses PCR followed by capillary electrophoresis for precise size determination of amplified fragments for forensic and population studies.
Q.30Hard
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?
Answer: C
Long-read sequencing can span repetitive sequences and detect large structural variations that short-reads cannot resolve, improving genome assembly quality.
Q.31Hard
What is the significance of the primer Tm (melting temperature) in multiplex PCR?
Answer: A
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.
Q.32Hard
CRISPR-Cas12 (Cpf1) differs from Cas9 in that it:
Answer: B
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.
Q.33Hard
In environmental metagenomic studies using 16S/18S rRNA amplicon sequencing, what is the primary limitation?
Answer: B
While 16S/18S rRNA is excellent for community profiling, limited sequence divergence at species level makes species-level discrimination challenging, requiring shotgun metagenomics for finer resolution.
Q.34Hard
In somatic gene therapy using ex vivo approach, which cell type is most commonly targeted for genetic modification?
Answer: B
Hematopoietic stem cells are preferred because they can self-renew, are easily accessible via bone marrow/blood, and can be reinfused to establish long-term therapeutic effects for blood disorders.
Q.35Hard
Which DNA technology is most suitable for detecting chromosomal abnormalities like deletions and duplications at the genomic level?
Answer: A
Array-CGH (aCGH) provides high-resolution detection of chromosomal imbalances across the entire genome, making it ideal for identifying deletions and duplications.
Q.36Hard
When designing a TaqMan probe for qPCR, what is the relationship between probe length and specificity in target detection?
Answer: B
TaqMan probes of 18-25 bp with Tm 5-10°C higher than primers provide optimal specificity and sensitivity by requiring perfect base pairing for nuclease cleavage.
Q.37Hard
In forensic DNA analysis using STR markers, what advantage do newer SNP-based methods provide over traditional STR typing for 2024-25 investigations?
Answer: B
SNP-based methods offer lower mutation rates (~10⁻⁸), enable ancestry inference, and work better with degraded DNA samples compared to STRs, making them valuable for cold cases.
Q.38Hard
Which PCR-based technique is specifically used to amplify and sequence unknown DNA flanking regions of known sequences?
Answer: B
Inverse PCR uses outward-facing primers on a circularized DNA template to amplify and sequence flanking regions of known sequences, useful for finding regulatory elements.
Q.39Hard
In GWAS (Genome-Wide Association Studies) using DNA microarrays, what statistical principle is applied to identify significant SNP-trait associations?
Answer: A
GWAS uses Chi-square tests with Bonferroni correction (or FDR correction) to account for multiple hypothesis testing across millions of SNPs and identify genome-wide significant associations.
Q.40Hard
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.
