Q.(a) There are two different farm lands, one where Bt-cotton crop was cultivated and the other where non Bt-cotton crop (indigenous) was cultivated. Farmers responsible for this experimental cultivation were free to use the farming practices of their choice. During the cultivation period, the data was collected with respect to the amount of pesticide used, water required for irrigation and at harvesting time, the crop productivity. Based on the data collected, a bar graph was plotted which is shown below. Answer the following questions:
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🔒 Start your 14-day free trial to unlock the full solution →Part (a)Concept understanding — Data Interpretation
Data Interpretation: Seeing the Story Behind the Numbers
Think of the last time you looked at a weather app. You saw a row of sun icons, a temperature graph that curved upward, and a percentage for rain. You didn't just see those symbols — you instantly understood that the afternoon would be hot and you should carry water. That act of moving from raw symbols to a meaningful conclusion is the heart of data interpretation.
What It Really Means
Data interpretation is the skill of reading, understanding, and explaining the meaning hidden inside tables, charts, graphs, and diagrams. It is not about doing arithmetic — it is about asking: What does this picture tell me? What is the trend? What is unusual? What conclusion can I draw?
In your NCERT textbooks for commerce and humanities, you will encounter data in many forms: a bar chart showing India's export growth over five years, a pie chart dividing household expenditure, a line graph of literacy rates across states, or a table of census figures. Your job is not to calculate percentages or sums — that is mathematics. Your job is to describe what you see, compare the parts, and infer the larger pattern or implication.
Data interpretation is a prose subject. You will never be asked to compute a number. You will be asked to write sentences like: "The graph shows a steady rise in exports from 2015 to 2019, with a sharp dip in 2020." The numbers are already given — you just have to read them correctly and put them into words.
Why It Matters for You
As a commerce or humanities student, you will spend your career making decisions based on data — whether you become an economist, a manager, a journalist, or a policy analyst. A table of sales figures is useless until someone interprets it: "Sales dropped in the third quarter because of the monsoon." A census table is just numbers until someone says: "The urban population is growing faster than the rural, which means cities need more schools."
Data interpretation is the bridge between raw information and real-world understanding. Without it, data is just noise. With it, you can spot trends, identify problems, and support arguments with evidence.
The Core Skills You Need
- Reading the axes and labels — Every graph has a title, an X-axis, a Y-axis, and a legend. You must know what each represents before you can say anything meaningful.
- Describing trends — Is the line going up, down, or staying flat? Is the bar taller this year than last? Use words like increase, decrease, fluctuate, peak, trough, steady, gradual, sharp.
- Making comparisons — Which category is largest? Which is smallest? How do two states compare? Use phrases like more than, less than, similar to, twice as much.
- Spotting exceptions — Is there a sudden jump or drop? A year that breaks the pattern? That is often the most important part to mention.
- Drawing a conclusion — What does the overall picture suggest? For example: "The data shows that female literacy has improved, but rural areas still lag behind urban areas."
Never invent numbers or statistics. The data is given to you — your job is to interpret what is already there, not to calculate new figures. If the table shows "45%", you say "45%". You do not convert it to a fraction or a decimal.
A Simple Example (Without Numbers)
Imagine a bar chart titled "Monthly Rainfall in Chennai." The bars are low from January to May, then shoot up in June, stay high through September, and drop again in October. You do not need to know the exact millimetres. You interpret: "Chennai receives most of its rainfall during the southwest monsoon months of June to September, with very little rain in the first half of the year."
That is data interpretation. You took a visual pattern and turned it into a clear, meaningful sentence.
Common Mistakes to Avoid
- Don't describe every single data point — That is just reading aloud. Instead, describe the overall pattern and mention only the most important highs, lows, or changes.
- Don't add your own opinions — "The government should do something about this" is not interpretation. Stick to what the data shows.
- Don't confuse correlation with causation — If two lines go up together, you can say they are related, but you cannot say one caused the other unless the data proves it. …
Part (b)Concept understanding — Recombinant DNA Technology
Imagine you have a cookbook with recipes from all over the world. Normally, you can only cook what's in one book at a time. But what if you could cut out the best recipe from one book and paste it into another, so your new book has a dish that no single cuisine ever had before? That is the basic idea behind Recombinant DNA Technology.
At its simplest, this technology is a way to take a piece of DNA (the genetic instruction manual) from one organism and join it with the DNA of a completely different organism. The result is a new, "recombinant" DNA molecule — a hybrid that never existed in nature. Think of it as genetic tailoring: you cut a gene from a human, a bacterium, or a plant, and stitch it into the DNA of another organism, often a bacterium or yeast. That host organism then reads the new instructions and starts producing the protein the inserted gene codes for.
Why does this matter? Because it lets us manufacture things that living organisms naturally make, but in a controlled, large-scale way. For example, the human insulin gene can be inserted into E. coli bacteria. These bacteria then become tiny factories, churning out human insulin that can be purified and given to diabetic patients. Before this technology, insulin had to be extracted from the pancreases of cows and pigs — a slow, expensive, and sometimes allergenic process.
The NCERT textbook (Class 12 Biology, Chapter 11) defines it precisely: Recombinant DNA Technology is the technique of joining DNA from two different species and inserting it into a host organism to produce a new genetic combination. The textbook highlights three key tools that make this possible:
- Restriction Enzymes – These are the "molecular scissors" that cut DNA at specific, predictable points. They allow scientists to cut out a desired gene cleanly.
- Vectors – These are the "delivery vehicles," usually plasmids (small circular DNA in bacteria) or viruses, that carry the foreign DNA into the host cell.
- Host Organisms – The living factory (like bacteria, yeast, or plant cells) that will replicate the recombinant DNA and produce the desired protein.
The core principle is genetic recombination — creating a DNA molecule that contains sequences from two or more different sources. This is not the same as natural reproduction or mutation; it is a deliberate, laboratory-made hybrid.
The process itself follows a clear sequence:
- Isolation of the desired gene (say, the human insulin gene) from the donor organism's DNA.
- Cutting both the gene and the vector DNA with the same restriction enzyme, creating matching "sticky ends."
- Ligation — using an enzyme called DNA ligase to permanently join the gene and the vector, forming the recombinant DNA.
- Transformation — inserting this recombinant DNA into a host cell (like a bacterium).
- Selection — identifying and growing only those host cells that successfully took up the recombinant DNA.
- Expression — getting the host cells to produce the desired protein in large quantities.
A common confusion is thinking this technology creates "new life." It does not. It creates a new genetic combination inside an existing living cell. The host organism remains the same species, but it now carries an extra instruction — like a factory that gets a new blueprint for a product it never made before. …
This case-based question compares Bt-cotton and non-Bt (indigenous) cotton on three parameters, and the bar graph carries a deliberate twist on the water reading.
Part (a)
(i) From the graph, Bt-cotton uses less pesticide and gives higher crop productivity, but requires more water for irrigation than non-Bt cotton. Reason: the Bt gene (cry gene from Bacillus thuringiensis) makes the plant produce a toxin against bollworm, so far fewer pesticide sprays are needed and yield is higher; the higher-yielding Bt variety, however, has a greater irrigation demand.
(ii) Where water is available, Bt-cotton is preferable — less pesticide, higher yield, so lower input cost and better returns. …
Part (a): Bt-cotton uses less pesticide and gives higher yield, but needs more water for irrigation than non-Bt cotton — so a Rajasthan (water-scarce) farmer prefers the non-Bt (indigenous) cotton because it requires less irrigation water. Part (b): EcoR I/BamH I/Hind III are restriction enzymes; antibiotic-resistance genes are the selectable markers (insertional inactivation); vectors replicate autonomously; ori is essential for replication; ligation at Hind III works but inactivates tet^R, so amp^R is used for selection.
Part (a)
(i) Interpretation of the three parameters.
The bar graph compares Bt-cotton with non-Bt (indigenous) cotton:
- Pesticide used — lower for Bt-cotton. The Bt gene (cry gene from Bacillus thuringiensis) makes the plant synthesise a Cry protein toxic to bollworm larvae, so far fewer chemical sprays are needed.
- Water for irrigation — HIGHER for Bt-cotton. This is the key twist in the graph: the high-yielding Bt variety has a greater irrigation demand than the indigenous crop.
- Crop productivity — higher for Bt-cotton, because reduced pest damage means less crop loss and a larger harvest.
(ii) Which crop I would cultivate, and why.
Where irrigation water is not a limiting factor, I would grow Bt-cotton: lower pesticide cost, higher yield and less chemical pollution outweigh its higher water need.
(iii) Which crop a Rajasthan farmer would prefer, and why. …
Showing the 12 most recent of 20 on this concept.
- CBSE 2026Set 57/1/11 markMCQQ.Which of the following statements about plasmids is incorrect ? (A) Plasmids have the ability to replicate within the bacterial cell. (B) Their replication is controlled by chromosomal DNA. (C) They are autonomously replicating circular extra-chromosomal DNA. (D) They often carry antibiotic resistant genes.
›Reveal solutionSolution
The incorrect statement about plasmids is that their replication is controlled by chromosomal DNA; plasmids replicate autonomously.
Plasmids are fascinating and crucial components in the world of microbiology and biotechnology. They are essentially small, circular, extra-chromosomal DNA molecules found predominantly in bacteria, but also in some eukaryotes like yeast. Think of them as accessory genetic units that carry non-essential but often beneficial genes for the host cell.
Let's break down the given statements to understand which one is incorrect:
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Statement (A): Plasmids have the ability to replicate within the bacterial cell.
This statement is correct. A defining feature of plasmids is their ability to self-replicate. They possess their own origin of replication (ori) sequence, which allows them to initiate DNA synthesis independently of the main bacterial chromosome. This autonomous replication is what makes them incredibly useful as vectors in genetic engineering, as they can multiply along with the host cell, carrying the inserted foreign DNA.
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Statement (B): Their replication is controlled by chromosomal DNA.
This statement is incorrect. As mentioned above, plasmids replicate autonomously. This means their replication is independent of the bacterial cell's main chromosomal DNA replication. While the host cell's machinery (enzymes, nucleotides) is used for plasmid replication, the initiation and control of plasmid replication are governed by sequences within the plasmid itself, not by the bacterial chromosome. This independence is a key distinction between plasmids and the main chromosome.
ImportantThe autonomous replication of plasmids, independent of the host cell's chromosomal DNA, is a fundamental characteristic that distinguishes them and makes them invaluable tools in molecular biology.
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Statement (C): They are autonomously replicating circular extra-chromosomal DNA.
This statement is correct. This is a precise definition of a plasmid.
- Autonomously replicating: They have their own origin of replication and can replicate independently.
- Circular: Most plasmids are found in a closed circular form. …
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- CBSE 2026Set 57/2/11 markMCQQ.Observe the contents 1, 2, 3 and 4 of soil samples I, II and III shown in the graph. If the temperature and moisture of all soil samples are identical, which soil sample(s) will show faster decomposition ? (A) Soil Sample I (B) Soil Sample II (C) Soil Sample III (D) Both Soil Samples II and III
›Reveal solutionSolution
Decomposition proceeds fastest in the soil sample with the largest population of detritivores and decomposers; based on the standard NCERT-style version of this question, that is Soil Sample II — though the platform does not have the original graph on file to confirm the exact values.
When organic matter — dead leaves, animal waste, plant litter — falls to the ground, it doesn't simply vanish. It is broken down through decomposition, a process driven by two groups of organisms working in concert: detritivores (earthworms, millipedes, woodlice) that physically fragment the material, and decomposers (bacteria and fungi) that chemically break down complex molecules into simpler nutrients the soil can absorb.
The speed of decomposition hinges on several factors. Temperature and moisture create the physical environment — warmth accelerates microbial activity, moisture keeps organisms hydrated and mobile. But given that all three soil samples in this question share identical temperature and moisture conditions, the deciding factor becomes the population of organisms doing the actual work — the contents 1-4 plotted in the source graph.
NoteThis platform does not have the original graph's numeric values on file, so the exact readings for contents 1-4 across Soil Samples I, II and III cannot be reproduced here. The reasoning below follows the general principle the question tests, applied to the typical pattern this style of NCERT question uses. …
- CBSE 2026Set 57/2/11 markMCQQ.Assertion (A) : DNA Ligase is used to join DNA fragments. Reason (R) : It catalyses the formation of glycosidic bonds between nucleotides. (A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation for Assertion (A). (B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not correct explanation for Assertion (A). (C) Assertion (A) is true, Reason (R) is false. (D) Assertion (A) is false, Reason (R) is true.
›Reveal solutionSolution
DNA Ligase joins DNA fragments by catalysing phosphodiester bonds, not glycosidic bonds. So Assertion is true, Reason is false — option (C).
The question tests a very specific piece of molecular biology: what bond does DNA Ligase actually form? Many students memorise "DNA Ligase joins fragments" but forget the exact chemistry. Let's break it down cleanly.
Why the Assertion is correct
DNA Ligase is the enzyme used in DNA replication, repair, and genetic engineering to seal nicks in the DNA backbone. It joins two DNA fragments — for example, an Okazaki fragment to the growing lagging strand, or an insert into a plasmid vector. This is a standard fact in biotechnology and molecular biology.
Why the Reason is wrong
The Reason claims DNA Ligase catalyses the formation of glycosidic bonds between nucleotides. That is a critical error.
- A glycosidic bond links a sugar (deoxyribose) to a nitrogenous base (A, T, G, C) — that bond is formed during nucleotide synthesis, not by DNA Ligase.
- DNA Ligase catalyses the formation of a phosphodiester bond between the 3'-hydroxyl group of one nucleotide and the 5'-phosphate group of the next nucleotide. This is the bond that holds the sugar-phosphate backbone together.
Watch outA common mistake is confusing "joining nucleotides" with "forming the bond between sugar and base." The bond between nucleotides in a DNA strand is always phosphodiester, never glycosidic.
Step-by-step reasoning
- Evaluate Assertion (A): "DNA Ligase is used to join DNA fragments." …
- CBSE 2026Set ANNUAL1 markMCQQ.Given below are the steps carried out to construct a recombinant DNA.(i) Isolation of genetic material(ii) Insertion of recombinant DNA in the host cell /organism(iii) Obtaining the foreign gene product(iv) Amplification of gene of interest(v) Downstream processing. Which one of the following gives the correct sequences of these steps?(a)(i)(iii)(iv)(ii)(v)(b)(i)(iv)(ii)(iii)(v)(c)(ii)(i)(iii)(iv)(v)(d)(ii)(iv)(v)(iii) (i)
›Reveal solutionSolution
Constructing and using recombinant DNA follows a fixed logical sequence: first isolate and amplify the gene of interest, then insert the recombinant DNA into a host, let the host express the gene product, and finally process that product for use — i.e., (i) → (iv) → (ii) → (iii) → (v).
Recombinant DNA technology (genetic engineering) involves several sequential processes:
- (i) Isolation of genetic material (DNA) — the DNA must first be extracted in a pure form from the source cell, free of other macromolecules.
- (iv) Amplification of the gene of interest — using restriction enzymes to cut out the desired gene and, typically, PCR to amplify it, then ligating it into a suitable vector to form the recombinant DNA.
- (ii) Insertion of the recombinant DNA into the host cell/organism — the recombinant DNA (vector + gene of interest) is introduced into a competent host cell (transformation) and the host is then cultured/multiplied so the gene is expressed. …
- CBSE 2025Set ANNUAL1 markMCQQ.Which one of the following is not required for rDNA technology ?(i) DNA polymerase(ii) DNA ligase(iii) Restriction endonuclease(iv) Reverse transcriptase
›Reveal solutionSolution
Basic recombinant DNA technology always needs a cutting enzyme (restriction endonuclease), a joining enzyme (DNA ligase) and DNA-copying capability (DNA polymerase, e.g. for PCR); reverse transcriptase is only needed in the special case of starting from an RNA/mRNA template, so it is the one "not required" in general.
The core enzyme toolkit of rDNA technology includes:
- Restriction endonucleases: "molecular scissors" that cut DNA at specific recognition sequences to isolate the gene of interest and to open up the vector for insertion — always required.
- DNA ligase: joins ("glues") the cut gene of interest into the vector DNA to form the recombinant DNA molecule — always required.
- DNA polymerase: needed for amplifying DNA (e.g. via PCR) and is also the enzyme the host cell itself uses to replicate the recombinant plasmid — required in essentially every rDNA procedure. …
- CBSE 2024Set 57/3/11 markMCQQ.Which native plasmid did Stanley Cohen and Herbert Boyer use for the construction of the first recombinant DNA ? (A) Salmonella typhimurium (B) Streptococcus pneumoniae (C) Escherichia coli (D) Haemophilus influenzae
›Reveal solutionSolution
The first recombinant DNA experiment used a plasmid from Salmonella typhimurium — specifically, a small, naturally occurring plasmid called pSC101 — which was cut with a restriction enzyme and spliced with foreign DNA. The correct option is (A).
The key to this question is remembering the historical landmark experiment by Cohen and Boyer in 1973. They weren't just using any E. coli plasmid — they deliberately chose a plasmid from a different bacterial species to demonstrate that recombinant DNA could be constructed across species boundaries.
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Why not E. coli?
E. coli does have plasmids (like the famous pBR322, developed later), but Cohen and Boyer wanted to prove that DNA from one organism could be stably inserted into the plasmid of another. Using an E. coli plasmid would have been less convincing — it might have been argued that the foreign DNA was just recombining with native E. coli sequences. So they picked a plasmid from a different bacterium: Salmonella typhimurium.
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The actual plasmid: pSC101
This plasmid was isolated from Salmonella typhimurium by Stanley Cohen. It was small (about 9.4 kb), had a single EcoRI restriction site, and carried a tetracycline-resistance gene — perfect for selection. Boyer’s team used EcoRI to cut both pSC101 and a piece of foreign DNA (from a frog or another bacterium), then ligated them together. The resulting recombinant plasmid was introduced into E. coli, where it replicated and expressed the foreign DNA.
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Why the other options are wrong …
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- CBSE 2024Set ANNUAL1 markMCQQ.DNA or RNA segment tagged with radioactive molecule is called –(a) Probe(b) Vector(c) Clone(d) Plasmid
›Reveal solutionSolution
A radioactively labelled DNA/RNA segment used to identify a complementary target sequence is called a molecular hybridisation probe.
In recombinant DNA technology, a probe is a single-stranded DNA or RNA sequence tagged with a radioactive isotope (e.g., ³²P), used to detect the presence of a complementary nucleotide sequence in a sample through molecular hybridisation (e.g., in Southern blotting, or colony hybridisation for screening a clone carrying the gene of interest).
…
- CBSE 2023Set TERM21 markMCQQ.A single strand of Nucleic acid tagged with a radioactive molecule is called:(a) Plasmid(b) Vector(c) Probe(d) Selectable marker
›Reveal solutionSolution
A single-stranded nucleic acid molecule tagged with a radioactive isotope, used to detect a complementary sequence, is called a probe.
In recombinant DNA technology, to confirm the presence of a specific gene or DNA sequence among many DNA fragments, a single-stranded DNA or RNA molecule complementary to that sequence is labelled with a radioactive isotope (commonly ³²P) — this labelled molecule is called a (radioactive) probe. It is used in techniques such as Southern/Northern hybridisation to specifically bind (hybridise) with its complementary sequence, which can then be detected by autoradiography. …
- CBSE 2023Set ANNUAL1 markMCQQ.The reagent that is used in the ELISA test is(a) polymerase(b) peroxidase(c) ligase(d) endonuclease
›Reveal solutionSolution
ELISA uses an enzyme such as peroxidase.
ELISA (Enzyme-Linked Immunosorbent Assay) detects an antigen or antibody by attaching an enzyme to a specific antibody. When the substrate is added, the enzyme catalyses a colour-producing reaction whose intensity indicates the amount of antigen present. Common reporter enzymes are horseradish peroxidase and alkaline phosph …
- CBSE 2022Set M1 markQ.What is the function of DNA ligase?
›Reveal solutionSolution
DNA ligase joins DNA fragments by sealing nicks with phosphodiester bonds.
DNA ligase catalyses the formation of a phosphodiester bond between adjacent nucleotides, thereby joining two DNA fragments (for example, joining a foreign DNA insert to a vector, or sealing Okazaki fragments during replication). I …
- CBSE 2022Set GO1 markQ.What is 'r' in rDNA?
›Reveal solutionSolution
'r' = recombinant; rDNA = recombinant DNA.
Concept. Recombinant DNA (rDNA) is an artificial DNA molecule created by combining a piece of foreign (donor) DNA with a vector DNA (such as a plasmid). The foreign gene is cut out with restriction endonucleases and joined to the cut vector by DNA ligase; the resulting hybrid molecule is the recombinant DNA. When i …
- CBSE 2019Set 57/2/11 markQ.Give two reasons as to why a weed such a Calotropis flourishes in abandoned fields.
›Reveal solutionSolution
Calotropis flourishes in abandoned fields primarily due to reduced competition from other plants and its inherent ability to tolerate harsh environmental conditions and deter herbivores.
Concept and Intuition
Weeds are often defined as "plants out of place," but from an ecological perspective, they are typically pioneer species or ruderals. These are plants that are excellent at colonizing disturbed or open habitats. Abandoned fields represent a classic example of such a disturbed habitat.
When a field is abandoned, the regular human interventions like tilling, weeding, irrigation, and fertilization cease. This creates an environment where:
- Competition changes: The dominant cultivated crops are no longer present, and the field is open for other plants to colonize.
- Environmental conditions can be harsh: The soil might be depleted of nutrients, exposed to intense sunlight, and prone to drought, as there's no active management to maintain optimal growing conditions.
- Herbivory pressure might increase: Without human protection, plants are more exposed to grazing animals.
Calotropis (commonly known as Aak or Madar) possesses specific biological traits that make it exceptionally well-suited to exploit these conditions, allowing it to thrive where many other plants would struggle.
Reasons for Flourishing
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Reduced Competition and Absence of Agricultural Practices:
In an abandoned field, the primary competitors—the cultivated crops—are no longer present. Farmers also cease practices like tilling, weeding, and herbicide application, which actively suppress weed growth. This creates an open niche with abundant resources (sunlight, space, water, and available nutrients) that Calotropis can readily exploit. As a fast-growing, opportunistic species, it can quickly establish itself and outcompete other early colonizers that might be less robust or slower growing. The lack of disturbance allows its root system to develop undisturbed and its aerial parts to grow without being cut back.
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Tolerance to Harsh Environmental Conditions and Effective Anti-Herbivory Mechanisms: …
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