#RNA analysis

PCR Modifications

Which technique is most suitable for quantifying mRNA levels?

Quantification of mRNA requires conversion of labile RNA into stable complementary DNA followed by exponential amplification and real-time detection. Reverse transcription using oligo-dT, random hexamers or gene-specific primers with reverse transcriptase generates cDNA proportional to original transcript abundance. Subsequent quantitative PCR measures Ct values inversely related to initial copy number, allowing relative or absolute quantification via standard curves and reference genes. Southern blotting detects DNA, FISH visualizes localization, and microarrays provide hybridization profiles

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Transcript analysis

Which technique is most suited for identifying the 5′ end of an RNA transcript?

Determination of the authentic 5 prime end of a transcript requires extension of a labeled primer annealed downstream. In primer extension, reverse transcriptase synthesizes complementary DNA until reaching the extreme 5 prime terminus of messenger RNA, generating product whose length indicates transcriptional start site. Northern blotting estimates size and abundance but lacks nucleotide resolution at ends. S1 mapping provides approximate termini, while 3 prime RACE specifically targets the polyadenylated tail. Therefore, primer extension remains a classical method of choice for high-resoluti

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Transcriptome analysis

Which statement is FALSE about poly(A) profiling?

Poly(A) profiling is a 3′-end focused transcriptomic method that captures and sequences regions adjacent to polyadenylation sites. By using oligo(dT)-based enrichment and sequencing of the 3′ termini, it identifies alternative polyadenylation events, novel transcripts defined by distinct 3′ ends, and can reveal 3′ UTR alterations associated with gene fusions. Stating that it analyzes 5′ ends misrepresents its design, since 5′ cap analysis is performed by CAGE, not poly(A) profiling. Therefore the claim of 5′ end analysis is inconsistent with its mechanistic foundation and primary applications.

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Transcriptome analysis

In the RPA (Ribonuclease Protection Assay), what is the function of RNase A and T1?

Ribonuclease Protection Assay relies on solution hybridization between a labeled antisense RNA probe and target mRNA, forming a double-stranded hybrid resistant to single-strand-specific ribonucleases. RNase A, which cleaves after cytosine and uridine residues, and RNase T1, which cleaves after guanosine, are added to digest all unhybridized single-stranded RNA, including excess probe and non-target RNAs. The protected double-stranded fragment remains intact and is resolved on denaturing PAGE. Quantification of its intensity reflects abundance of specific transcript, allowing sensitive detecti

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Blotting Techniques

Northern blotting is ideal to study:

Northern blotting preserves information about transcript length and abundance, making it particularly suited to study RNA splicing regulation. Pre-mRNA can undergo alternative exon inclusion, intron retention, exon skipping, or use of alternative 5' and 3' splice sites, generating multiple mature mRNAs of differing sizes from single gene. Formaldehyde agarose electrophoresis resolves these size variants, and probe hybridization reveals pattern of isoforms. Emergence of larger bands exclusively under induced condition indicates activation of splicing factors or retention events, insight not obt

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Blotting Techniques

Which blot uses RNA as the target molecule?

Northern blotting is historically named by analogy to Southern blotting and is dedicated to RNA target analysis. Total cellular RNA or poly(A) enriched mRNA is denatured with formaldehyde or glyoxal to eliminate secondary structures and separated on agarose gel according to length. After capillary or electro-transfer to positively charged nylon membrane and UV crosslinking, transcripts are hybridized with labeled antisense DNA or RNA probes. Autoradiographic signal indicates transcript size and abundance. Although largely supplanted by quantitative RT-PCR and RNA sequencing for sensitivity, No

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

View Details