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Q99 (IAS/2019) Science & Technology › Biotechnology & Health › Genetic engineering basics Official Key

What is Cas9 protein that is often mentioned in news?

Result
Your answer: —  ·  Correct: A
Explanation

The Cas9 enzyme acts like molecular scissors, making a double-strand cut at the specified site once the gRNA binds to the target DNA[1]. The function of Cas9 has been manipulated to precisely insert or remove specific DNA fragments from a strand of genetic material, acting as a pair of molecular scissors[2]. This makes Cas9 a crucial tool in CRISPR gene editing technology, where site-specific DNA double-strand breaks (DSBs) are induced by the Cas9 protein under the control of sg-RNA, triggering DNA repair mechanisms[3].

Option B is incorrect because while biosensors can detect DNA and pathogens, Cas9 itself is not used as a biosensor. Option C is incorrect because Cas proteins have been utilized for genome editing in plants and animals to create modified pest-resistant plants[4], but Cas9 is a protein tool used for editing, not a gene itself. Option D is incorrect because Cas9 is not a herbicidal substance; it is a protein enzyme used in the gene editing process to make precise cuts in DNA sequences.

Sources
  1. [3] https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2023.1133036/full
  2. [4] https://www.nabard.org/auth/writereaddata/tender/pub_3110250538571878.pdf
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Q. What is Cas9 protein that is often mentioned in news? [A] A molecular scissors used in targeted gene editing [B] A biosensor used in th…
At a glance
Origin: Mostly Current Affairs Fairness: Low / Borderline fairness Books / CA: 0/10 · 7.5/10
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This is a classic 'Term in News' question. While static books (NCERT) explain DNA and heredity, they don't cover specific new proteins like Cas9. This question rewards the 'Newspaper Reader' over the 'Bookworm'. If a science term is in the headlines (CRISPR was massive news), you must know its one-line functional analogy.

How this question is built

This question can be broken into the following sub-statements. Tap a statement sentence to jump into its detailed analysis.

Statement 1
Is Cas9 protein a molecular "scissors" used for targeted gene editing?
Origin: Web / Current Affairs Fairness: CA heavy Web-answerable

Web source
Presence: 5/5
"Once the gRNA binds to the target DNA, the Cas9 enzyme acts like molecular scissors, making a double-strand cut at the specified site (Doudna & Charpentier, 2014)."
Why this source?
  • Explicitly describes Cas9 as acting "like molecular scissors" to make a double-strand cut at the targeted site.
  • Connects the cut by Cas9 to targeted editing via guide RNA and cellular repair pathways that alter gene function.
Web source
Presence: 5/5
"function of Cas9 has been manipulated to precisely insert or remove specific DNA fragments from a strand of genetic material, acting as a pair of molecular scissors."
Why this source?
  • States Cas9 has been manipulated to insert or remove DNA fragments, describing it as "acting as a pair of molecular scissors."
  • Frames Cas9's role directly in precision editing (inserting/removing DNA), matching the metaphor of molecular scissors for targeted editing.
Web source
Presence: 5/5
"Site-specific DNA double-strand breaks (DSBs), which are induced by the Cas9 protein under the control of sg-RNA, trigger DNA repair mechanisms."
Why this source?
  • Explains that Cas9, guided by sgRNA, induces site-specific DNA double-strand breaks (DSBs).
  • Shows the mechanistic basis (targeted cleavage) by which Cas9 enables gene editing, supporting the "scissors" metaphor.

Indian Economy, Nitin Singhania .(ed 2nd 2021-22) > Chapter 9: Agriculture > GENETICALLY MODIFIED (GM) CROPS > p. 301
Strength: 5/5
“• According to WHO, Genetically Modified Organisms (GMO) are the plants, animals or microorganisms in which the hereditary material (DNA) is altered in a manner that does not happen normally by mating or potentially regular recombination. It is also known as modern biotechnology/gene technology.• When genetic modification of a plant is performed, foreign gene (transgene) or gene of some other organism is artificially inserted into the plant's own genes. This is gene modification.”
Why relevant

Defines genetic modification as altering hereditary material (DNA) and inserting foreign genes — showing that deliberate changes to DNA underlie gene editing.

How to extend

A student can combine this with the idea of a tool that makes precise DNA changes (e.g., a molecular 'scissor' that cuts DNA at chosen sites) to see why a DNA-cutting protein would be useful for targeted modification.

Science , class X (NCERT 2025 ed.) > Chapter 8: Heredity > 8.2.3 How do these Traits get Expressed? > p. 131
Strength: 4/5
“How does the mechanism of heredity work? Cellular DNA is the information source for making proteins in the cell. A section of DNA that provides information for one protein is called the gene for that protein. How do proteins control the characteristics that we are discussing here? Let us take the example of tallness as a characteristic. We know that plants have hormones that can trigger growth. Plant height can thus depend on the amount of a particular plant hormone. The amount of the plant hormone made will depend on the efficiency of the process for making it. Consider now an enzyme that is important for this process.”
Why relevant

Explains that a gene (DNA segment) encodes proteins and that enzymes influence biological traits, linking changes in DNA to changes in cellular function.

How to extend

Knowing DNA sections map to traits, a student could infer that cutting or altering a specific gene could change the encoded protein and thus the trait — suggesting a role for a precise DNA-cutting agent.

Science , class X (NCERT 2025 ed.) > Chapter 7: How do Organisms Reproduce? > 7.1 DO ORGANISMS CREATE EXACT COPIES OF THEMSEL THEMSELVES? > p. 113
Strength: 4/5
“Organisms look similar because their body designs are similar. If body designs are to be similar, the blueprints for these designs should be similar. Thus, reproduction at its most basic level will involve making copies of the blueprints of body design. In Class IX, we learnt that the chromosomes in the nucleus of a cell contain information for inheritance of features from parents to next generation in the form of DNA (Deoxyribo Nucleic Acid) molecules. The DNA in the cell nucleus is the information source for making proteins. If the information is changed, different proteins will be made. Different proteins will eventually lead to altered body designs.”
Why relevant

States that changing DNA information leads to different proteins and altered organisms, emphasizing that targeted DNA changes can have predictable effects.

How to extend

A student can reason that a molecular mechanism that makes targeted cuts or edits in DNA would enable those predictable changes, supporting the plausibility of a 'scissors' for editing.

Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 16: Conservation Efforts > 16.17. DNA BARCODING > p. 248
Strength: 4/5
“A MoU signed between Zoological Survey of India (ZSI), a subordinate organization under MoEF&CC, and International Barcode of Life (iBOL), a Canadian not-for-profit corporation. ZSI and iBOL have come together for further efforts in DNA barcoding, a methodology for rapidly and accurately identifying species by sequencing a short segment of standardized gene regions and comparing individual sequences to a reference database. iBOL is a research alliance involving nations that have committed both human and financial resources to enable expansion of the global reference database, the development of informatics platforms, and/or the analytical protocols needed to use the reference library to inventory, assess, and describe biodiversity.”
Why relevant

Describes DNA barcoding and sequencing of specific gene regions, highlighting that specific DNA sequences can be identified and targeted.

How to extend

Combining sequence-identification (targeting) with a DNA-modifying tool suggests how a sequence-specific 'cutting' protein could be directed to particular genes for editing.

Science , class X (NCERT 2025 ed.) > Chapter 8: Heredity > separate traits, shape and colour of seeds Figure 8.5 > p. 132
Strength: 3/5
“inherited. This is explained by the fact that each gene set is present, not as a single long thread of DNA, but as separate independent pieces, each called a chromosome. Thus, each cell will have two copies of each chromosome, one each from the male and female parents. Every germcell will take one chromosome from each pair and these may be of either maternal or paternal origin. When two germ cells combine, they will restore the normal number of chromosomes in the progeny, ensuring the stability of the DNA of the species. Such a mechanism of inheritance explains the results of the Mendel experiments, and is used by all sexually reproducing organisms.”
Why relevant

Explains that genes exist as discrete pieces (chromosomes) and that inheritance depends on specific DNA units, implying genes are addressable units.

How to extend

A student could extend this by noting that addressable gene units make it meaningful to target and cut particular DNA loci with a molecular tool to alter inheritance or traits.

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