Bioinformatics- ICAR JRF/SRF 2024

• Chromosome Walking Technique:
• Chromosome walking is a positional cloning technique used to isolate and characterize a specific gene of interest when its exact chromosomal locus is known relative to a linked DNA marker.
• Methodology:
• Begins with a cloned DNA fragment close to the target gene as a probe to screen a genomic library for overlapping clones.
• The end of the newly isolated overlapping clone is then sequenced and used as a probe to 'walk' to the next adjacent clone in the genomic library.
• Successive rounds of hybridization walk systematically along the chromosome until the target gene is reached and isolated.
• Conclusion: Used to Locate and isolate specific genes within a chromosome (Option 1).

Correct option: (1) Locate and isolate specific genes within a chromosome

• Small Non-Coding RNA Molecules in Gene Regulation:
• RNA interference (RNAi): The overarching pathway of sequence-specific post-transcriptional gene regulation mediated by short non-coding regulatory RNAs.
• MicroRNAs (miRNAs): Endogenously expressed ~21-23 nt non-coding RNAs that bind imperfectly to the 3' UTR of target mRNAs, causing translational repression or mRNA destabilization.
• Antisense RNA: Synthetic or natural regulatory RNA molecules complementary to mRNA transcripts that block translation or recruit RNase H.
• Small interfering RNAs (siRNAs): Exogenous or synthetic ~20-25 nt double-stranded RNA molecules that direct sequence-specific cleavage of target mRNAs via the RISC endonuclease Argonaute.
• Conclusion: All four techniques involve small RNA molecules: (A), (B), (C) and (D) (Option 3).

Correct option: (3) (A), (B), (C) and (D).

• Regulatory Functions of Non-Coding RNA (ncRNA):
• Non-coding RNAs (ncRNAs) do not encode proteins but play fundamental roles in controlling gene expression at multiple epigenetic, transcriptional, and post-transcriptional levels.
• Mechanisms of Action:
• microRNAs (miRNAs) and siRNAs modulate translation and direct mRNA cleavage.
• Long non-coding RNAs (lncRNAs) (e.g., Xist, HOTAIR) recruit chromatin remodeling complexes, act as transcriptional scaffolds, and regulate alternative splicing.
• piRNAs silence transposable elements in germline cells.
• Conclusion: Non-coding RNA can modulate transcription and translation through various mechanisms (Option 1).

Correct option: (1) Non-coding RNA can modulate transcription and translation through various mechanisms