What is the common examiner trap about Science & Tech in UPSC exams?

They may confuse 'nonsense mutation' with other mutation types (missense, frameshift) or swap 'prime editing' with older techniques like CRISPR-Cas9 or base editing. They might also ask about the total number of human tRNA genes (418) versus the number of optimized tRNAs (4) used in the study.

What should UPSC aspirants remember about Science & Tech for Prelims?

1. Target this Data: Nonsense mutations account for ~25% of disease-causing genetic changes. 2. Target this Nodal Body: Broad Institute, Harvard University, and University of Minnesota (research institutions). 3. Target this Technique: Prime-Editing-mediated Readthrough of premature Termination codons (PERT).

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PERT Gene-Editing Strategy: Prime Editing Targets 25% of Genetic Disorders via Nonsense Mutations

Q: Which of the following is a common viral vector used in gene therapy, as mentioned in the PERT study for delivering editing components into mice?

Adeno-Associated Virus 9 (AAV9), The article specifies that AAV9, a harmless virus repurposed as a delivery vehicle, was used to deliver prime-editing components into newborn mice in the study. AAV vectors are commonly used in gene therapy due to their low pathogenicity and ability to target various tissues.

Q: Consider the following statements regarding the PERT genome-editing strategy: 1. It is designed to treat genetic disorders caused by nonsense mutations, which account for about one-quarter of all known disease-causing genetic changes. 2. The strategy uses CRISPR-Cas9 to directly cut and repair the faulty DNA sequence causing the premature stop codon. 3. In mouse models, PERT restored enzyme activity levels between 1.7% and 7% in key organs, which is considered sufficient to reduce disease severity. Which of the statements given above is/are correct?

Both 1 and 3, Statement 1 is correct: Nonsense mutations account for ~25% of disease-causing changes. Statement 2 is incorrect: PERT uses prime editing (not CRISPR-Cas9), which does not create double-strand breaks but directly writes new genetic code. Statement 3 is correct: The article states that 1.7-7% restoration in mouse models is known to meaningfully reduce disease severity.

Q: According to the study published in Nature, what was the editing efficiency achieved by the PERT method in cultured human cells?

60-80%, The article clearly states that the PERT combination (PE6c enzyme with PE3 strategy) achieved 60-80% editing efficiency in cultured human cells, which is unusually high for multi-base genomic edits. It contrasts this with the typical 10-20% efficiency of homology-directed repair.

Q: What is the primary advantage of the PERT strategy over conventional approaches for treating genetic disorders caused by nonsense mutations?

It offers a single, gene-agnostic therapy for multiple disorders, avoiding the need for separate treatments for each mutation., The core innovation of PERT is its 'gene-agnostic' nature. Instead of designing a unique therapy for each specific nonsense mutation (a slow and expensive process), PERT aims to treat many such disorders with a single editing strategy by reprogramming a universal cellular component (tRNA) to override premature stop signals.

Science & Tech Health & EducationHIGH

Target:UPSC GS-IIIMPSCTeachingSSC GAPrelims HighMains High

17 Feb 2026

~2 min

Source: The Hindu

Key Data:~25% of genetic disorders60-80% editing efficiency418 tRNA genes1.7-7% enzyme restoration in mice

Bodies:Broad InstituteHarvard UniversityUniversity of MinnesotaCSIR-Institute of Genomics and Integrative Biology

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What This Article Covers

1.PERT (Prime-Editing-mediated Readthrough of premature Termination codons) is a new genome-editing strategy to treat disorders caused by nonsense mutations.

2.Nonsense mutations, which insert a premature stop signal in protein production, account for about 25% of all known disease-causing genetic changes.

3.The method converts a non-essential human tRNA gene into a 'suppressor tRNA' using prime editing (PE6c enzyme with 60-80% efficiency), restoring protein function in cell and mouse models without disrupting normal cellular processes.

The Big Picture

Prelims · HighMains · High

A breakthrough gene-editing strategy, PERT, has been developed to treat multiple genetic disorders caused by 'nonsense mutations'—which account for 25% of all disease-causing genetic changes. Instead of separate therapies for each mutation, this single approach reprograms the body's own tRNA to override premature stop signals, restoring protein function. This represents a significant leap toward 'gene-agnostic' therapy for rare diseases.

Exam Lens

Quick Exam Facts From News

Disease ShareNonsense mutations cause ~25% of genetic disorders

Editing EfficiencyPERT achieved 60-80% editing efficiency in cells

Key EnzymePE6c (prime editing enzyme)

Human tRNA Genes418 total tRNA genes in human cells

1-Minute Revision

›Disease Share: Nonsense mutations cause ~25% of genetic disorders
›Editing Efficiency: PERT achieved 60-80% editing efficiency in cells
›Target this Data: Nonsense mutations account for ~25% of disease-causing genetic changes.
›Target this Nodal Body: Broad Institute, Harvard University, and University of Minnesota (research institutions).
›Target this Technique: Prime-Editing-mediated Readthrough of premature Termination codons (PERT).

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News Snapshot

🧬

Gene-Agnostic Therapy

PERT strategy aims to treat multiple genetic disorders with a single editing approach, moving away from disease-specific treatments.

⚙️

Prime Editing Breakthrough

Using PE6c enzyme and optimized pegRNAs, researchers achieved high-efficiency (60-80%) editing of tightly folded tRNA genes.

🐭

In Vivo Validation

In mouse models of Hurler syndrome, PERT restored 1.7-7% of normal enzyme activity in brain, heart, and liver—levels known to reduce disease severity.

Detailed Analysis & Strategic Depth

Context / Background

Genetic disorders like cystic fibrosis and Batten disease often stem from 'nonsense mutations'—single DNA errors that insert a premature stop codon, halting protein production. Currently, each such mutation requires a separate, costly therapy designed from scratch. This fragmented approach is inefficient for treating the ~25% of genetic diseases caused by these mutations, highlighting the need for a universal solution.

Core Analysis & Implications

The PERT strategy leverages the redundancy of human tRNA genes (418 total) by using prime editing to convert a non-essential tRNA into a 'suppressor tRNA.' This engineered molecule reads through premature stop signals (like TAG) and inserts an amino acid, allowing complete protein synthesis. Critically, PERT showed high specificity—ignoring faulty stops while respecting natural termination signals—and restored 17-70% of normal enzyme activity in cell models of Batten, Tay-Sachs, and Niemann-Pick C1 diseases.

Technical Innovation & Safety

The research involved engineering thousands of tRNA variants for stability and efficiency, designing a library of 17,000 pegRNAs to access compact DNA regions, and developing the PE6c enzyme for high-efficiency editing. Safety tests confirmed no off-target DNA alterations, no disruption of global protein production, and no toxicity in treated mice—key hurdles for clinical translation.

Future Outlook / Way Forward

While promising, challenges remain in delivery, long-term safety, and tissue-specific performance across the human body. The use of AAV9 viral vectors for in vivo delivery aligns with existing gene-therapy approaches, providing a viable clinical pathway. As the first base-editing clinical trial this year targeted a TAG stop codon, PERT could accelerate the development of gene-agnostic therapies for rare diseases, potentially reducing development time and costs significantly.

Key Facts at a Glance

Disease ShareNonsense mutations cause ~25% of genetic disorders

Editing EfficiencyPERT achieved 60-80% editing efficiency in cells

Key EnzymePE6c (prime editing enzyme)

Human tRNA Genes418 total tRNA genes in human cells

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Practice exam-style questions based on this article.

Q1Static LinkageEasyUPSC, SSC, State PSC

Which of the following is a common viral vector used in gene therapy, as mentioned in the PERT study for delivering editing components into mice?

Q2Statement-basedHardUPSC

Consider the following statements regarding the PERT genome-editing strategy:

1. It is designed to treat genetic disorders caused by nonsense mutations, which account for about one-quarter of all known disease-causing genetic changes.

2. The strategy uses CRISPR-Cas9 to directly cut and repair the faulty DNA sequence causing the premature stop codon.

3. In mouse models, PERT restored enzyme activity levels between 1.7% and 7% in key organs, which is considered sufficient to reduce disease severity.

Which of the statements given above is/are correct?

Q3Data-centricMediumUPSC, SSC

According to the study published in Nature, what was the editing efficiency achieved by the PERT method in cultured human cells?

Q4Application/ImpactMediumUPSC, SSC, State PSC

What is the primary advantage of the PERT strategy over conventional approaches for treating genetic disorders caused by nonsense mutations?

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PERT Gene-Editing Strategy: Prime Editing Targets 25% of Genetic Disorders via Nonsense Mutations

Exam Lens

Quick Exam Facts From News

1-Minute Revision

News Snapshot

Gene-Agnostic Therapy

Prime Editing Breakthrough

In Vivo Validation

Detailed Analysis & Strategic Depth

Context / Background

Core Analysis & Implications

Technical Innovation & Safety

Future Outlook / Way Forward

Prelims Flashpoints

Key Facts at a Glance