UPSC NDA-1

11. Which of the following statements about DNA is/are correct ? 1. DNA

Which of the following statements about DNA is/are correct ?

  • 1. DNA is the hereditary material of all living organisms.
  • 2. All segments of DNA code for synthesis of proteins.
  • 3. Nuclear DNA is double helical with two nucleotide chains which run anti-parallel.
  • 4. DNA is also found in mitochondria.

Select the correct answer using the code given below :

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1, 2 and 3 only
3 and 4 only
1, 3 and 4 only
4 only
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Let’s evaluate each statement:
1. DNA is the hereditary material of all living organisms. This is incorrect. While DNA is the hereditary material for most organisms (bacteria, archaea, eukaryotes), some viruses use RNA as their genetic material.
2. All segments of DNA code for synthesis of proteins. This is incorrect. Large portions of DNA in eukaryotic genomes are non-coding. This includes regulatory sequences, introns (non-coding regions within genes), repetitive DNA, telomeres, etc.
3. Nuclear DNA is double helical with two nucleotide chains which run anti-parallel. This is correct. The Watson-Crick model describes DNA as a double helix where the two polynucleotide strands are complementary and run in opposite directions (5′ to 3′ and 3′ to 5′).
4. DNA is also found in mitochondria. This is correct. Mitochondria (and chloroplasts in plants) contain their own circular DNA (mtDNA), which is distinct from the nuclear DNA.
Based on the analysis, statements 3 and 4 are correct.
– DNA is the primary genetic material, but not universal (some viruses use RNA).
– Not all DNA sequences are protein-coding.
– Nuclear DNA is a double helix with anti-parallel strands.
– Extranuclear DNA exists in organelles like mitochondria and chloroplasts.
Mitochondrial DNA (mtDNA) is typically circular and much smaller than nuclear DNA. It encodes some proteins involved in cellular respiration, as well as ribosomal RNAs and transfer RNAs used within the mitochondrion. Due to its maternal inheritance pattern in many species, mtDNA is useful in tracing evolutionary lineages.

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12. Which one of the following is the chemical name for baking soda ?

Which one of the following is the chemical name for baking soda ?

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Sodium bicarbonate (Sodium hydrogen carbonate)
Sodium carbonate
Potassium bicarbonate (Potassium hydrogen carbonate)
Potassium carbonate
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Baking soda is a common household chemical used as a leavening agent in baking, as a cleaning agent, and for various other purposes. Its chemical formula is NaHCO₃. The chemical name for NaHCO₃ is Sodium bicarbonate, also known as Sodium hydrogen carbonate.
– Baking soda chemical formula: NaHCO₃.
– Chemical names: Sodium bicarbonate or Sodium hydrogen carbonate.
Sodium carbonate (Na₂CO₃) is known as washing soda. Potassium bicarbonate (KHCO₃) and Potassium carbonate (K₂CO₃) are related compounds but are not what is commonly referred to as baking soda.

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13. Which one of the following oxides of nitrogen is known as ‘anhydride’

Which one of the following oxides of nitrogen is known as ‘anhydride’ of nitric acid ?

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N<sub>2</sub>O
N<sub>2</sub>O<sub>3</sub>
NO<sub>2</sub>
N<sub>2</sub>O<sub>5</sub>
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An acid anhydride is a compound that reacts with water to form an acid. The anhydride of nitric acid (HNO₃) is formed by removing water from one or more molecules of the acid.
The formula for nitric acid is HNO₃. Taking two molecules and removing one water molecule:
2HNO₃ → H₂N₂O₆
H₂N₂O₆ – H₂O → N₂O₅
Thus, N₂O₅ (dinitrogen pentoxide) is the anhydride of nitric acid. It reacts with water to form nitric acid: N₂O₅ + H₂O → 2HNO₃.
– Anhydride: A compound that yields an acid when combined with water.
– To find the anhydride of an acid (like HNO₃), remove water molecule(s) from the acid formula while maintaining the correct ratio of other elements.
– N₂O₅ is dinitrogen pentoxide.
Similarly, the anhydride of sulfuric acid (H₂SO₄) is SO₃ (SO₃ + H₂O → H₂SO₄). The anhydride of carbonic acid (H₂CO₃) is CO₂ (CO₂ + H₂O ⇌ H₂CO₃). Oxides of non-metals are often acidic anhydrides.

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14. Which one of the following is a conventional energy source ?

Which one of the following is a conventional energy source ?

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Tidal energy
Geothermal energy
Solar energy
Biomass energy
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Conventional energy sources are generally considered to be those that are well-established, widely used on a large scale, and often (though not always) exhaustible. This category typically includes fossil fuels (coal, oil, gas), nuclear energy, and large-scale hydropower. Non-conventional or renewable energy sources are those that are naturally replenished and often rely on newer technologies for large-scale exploitation, such as solar, wind, tidal, geothermal, and modern biomass.
Among the given options, Tidal, Geothermal, and Solar energy are unequivocally classified as non-conventional/renewable energy sources. Biomass energy, particularly in the form of traditional uses like burning wood for fuel, has been used by humans for millennia and represents a long-established energy source, though often referred to as ‘traditional non-commercial’ energy. While modern biomass energy (e.g., bioelectricity, biofuels) is considered renewable/non-conventional, the term ‘biomass energy’ can encompass traditional use. In the context of the options provided, biomass has the longest history of widespread conventional use compared to the other listed sources, making it the most likely intended conventional source among these options, despite modern classifications.
– Conventional energy sources: Fossil fuels, Nuclear, Large Hydro.
– Non-conventional/Renewable energy sources: Solar, Wind, Tidal, Geothermal, Biomass, Small Hydro.
– The classification can sometimes be nuanced, especially regarding traditional biomass use versus modern biomass technologies.
Biomass energy refers to energy derived from organic matter. Its use ranges from traditional burning of wood and agricultural waste (especially in rural areas) to modern technologies like biogas plants, biomass power plants, and biofuel production. The long history of traditional biomass use contrasts with the relatively recent large-scale development of solar, wind, tidal, and geothermal power generation technologies. This historical context likely explains its inclusion as a potential ‘conventional’ source in this specific question, even though it falls under the ‘renewable’ category in modern classifications.

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15. A pencil is placed upright at a distance of 10 cm from a convex lens o

A pencil is placed upright at a distance of 10 cm from a convex lens of focal length 15 cm. The nature of the image of the pencil will be

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real, inverted and magnified
real, erect and magnified
virtual, erect and reduced
virtual, erect and magnified
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A convex lens has a positive focal length, f = 15 cm. The object (pencil) is placed at a distance u = 10 cm from the lens. Since the object is placed in front of the lens, u = -10 cm (using standard sign convention).
For a convex lens, when the object is placed between the optical centre and the principal focus (i.e., 0 < |u| < f, or 0 < 10 cm < 15 cm), the image formed is virtual, erect, and magnified.
– Convex lens image formation depends on object position relative to F (focus) and 2F.
– Object between optical centre and F: Image is virtual, erect, magnified, and on the same side as the object.
Using the lens formula 1/f = 1/v – 1/u:
1/15 = 1/v – 1/(-10)
1/15 = 1/v + 1/10
1/v = 1/15 – 1/10 = (2 – 3)/30 = -1/30
v = -30 cm.
Since v is negative, the image is virtual and formed on the same side as the object.
Magnification m = v/u = -30 / -10 = +3.
Since m is positive, the image is erect. Since |m| > 1, the image is magnified.
Thus, the image is virtual, erect, and magnified.

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16. An object is placed at the centre of curvature of a concave mirror of

An object is placed at the centre of curvature of a concave mirror of focal length 16 cm. If the object is shifted by 8 cm towards the focus, the nature of the image would be

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real and magnified
virtual and magnified
real and reduced
virtual and reduced
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A concave mirror of focal length f = 16 cm has its centre of curvature (C) at a distance 2f = 32 cm from the mirror. Initially, the object is placed at C (u = 32 cm). When the object is at C, the image is formed at C, is real, inverted, and of the same size.
The object is shifted by 8 cm towards the focus (which is at 16 cm). The new object distance is u’ = 32 cm – 8 cm = 24 cm.
The object is now located between the centre of curvature (32 cm) and the focus (16 cm). For a concave mirror, when the object is placed between C and F, the image formed is real, inverted, and magnified.
– Concave mirror image formation depends on object position relative to F (focus) and C (centre of curvature).
– Object at C: Image at C, real, inverted, same size.
– Object between C and F: Image beyond C, real, inverted, magnified.
The mirror formula is 1/f = 1/v + 1/u. Using f = 16 cm and u = 24 cm, we can calculate the image distance v:
1/16 = 1/v + 1/24
1/v = 1/16 – 1/24 = (3 – 2)/48 = 1/48
v = 48 cm.
Since v is positive, the image is real and formed in front of the mirror, beyond C (at 32 cm).
The magnification m = -v/u = -48/24 = -2.
The negative sign indicates an inverted image, and |m| > 1 indicates a magnified image. Thus, the image is real, inverted, and magnified.

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17. Consider the following statements : 1. Rajmahal highlands consist of

Consider the following statements :

  • 1. Rajmahal highlands consist of lava flow deposits.
  • 2. Bundelkhand gneiss belong to the oldest Achaean rocks of India.

Which of the statements given above is/are correct ?

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1 only
2 only
Both 1 and 2
Neither 1 nor 2
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Statement 1 is correct. The Rajmahal Hills in Eastern India are composed primarily of basaltic lava flows known as the Rajmahal Traps, which erupted during the Jurassic period.
Statement 2 is correct. The Bundelkhand Gneissic Complex is a part of the Peninsular Gneiss and belongs to the Archaean geological period, making it one of the oldest rock formations in India.
Since both statements are correct, the correct option is C.
– Rajmahal Traps: Large igneous province formed by volcanic activity.
– Bundelkhand Gneiss: Ancient crystalline basement rocks.
– Archaean Eon: The earliest geological eon in Earth’s history, preceding the Proterozoic Eon.
The Deccan Traps, another major large igneous province formed by lava flows, are younger than the Rajmahal Traps, dating back to the Cretaceous-Paleogene boundary. The Bundelkhand region is a shield area composed of granite and gneiss, representing the core of the Indian Peninsular plate.

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18. The Nagarjuna Sagar Project is located on which one of the following r

The Nagarjuna Sagar Project is located on which one of the following rivers ?

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Godavari
Krishna
Kavery
Mahanadi
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The correct answer is B) Krishna.
The Nagarjuna Sagar Project, which includes a major dam and reservoir, is constructed across the Krishna River.
The Nagarjuna Sagar Dam is located between the states of Telangana and Andhra Pradesh in India. It is one of the earliest and largest dam projects built in independent India, primarily for irrigation and hydroelectric power generation. The project is named after the Buddhist scholar and philosopher Acharya Nagarjuna.

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19. Which of the commonly used household item(s) release Bisphenol A (BPA)

Which of the commonly used household item(s) release Bisphenol A (BPA) which is an endocrine disruptor and bad for human health?

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  • 1. Steel utensils
  • 2. Plastic coffee mugs
  • 3. Aluminium utensils
  • 4. Plastic water storage bottles

Select the correct answer using the code given below:

1 only
1 and 2 only
2 and 4 only
1, 2 and 3 only
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The correct answer is C) 2 and 4 only.
Bisphenol A (BPA) is a chemical used in the production of polycarbonate plastics and epoxy resins. Polycarbonate plastic is commonly used in making hard plastic items like reusable water bottles and some coffee mugs. Epoxy resins are often used as internal coatings for food and beverage cans and metal lids.
– **Steel utensils (1):** Typically made of stainless steel and do not contain BPA.
– **Plastic coffee mugs (2):** Many rigid plastic mugs, especially older or cheaper ones, are made from polycarbonate plastic which can leach BPA, particularly when hot liquids are used.
– **Aluminium utensils (3):** Generally made of aluminium metal. While some aluminium cans or containers might have epoxy resin linings containing BPA, standard aluminium cooking or eating utensils do not typically contain BPA.
– **Plastic water storage bottles (4):** Reusable hard plastic water bottles (often labeled with recycling code 7, though not exclusively) are frequently made from polycarbonate and are known sources of BPA leaching. Many manufacturers now produce “BPA-free” versions.
Therefore, plastic coffee mugs and plastic water storage bottles are the most likely common household items from this list to release BPA.

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20. Which one of the following is a reduction reaction?

Which one of the following is a reduction reaction?

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2 Mg (s) + O₂ (g) → 2 MgO (s)
S (s) + O₂ (g) → SO₂ (g)
2 HgO (s) $xrightarrow{heat}$ 2 Hg (l) + O₂ (g)
Mg (s) + S (s) → MgS (s)
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The correct answer is C) 2 HgO (s) $\xrightarrow{heat}$ 2 Hg (l) + O₂ (g).
Reduction is a chemical process that involves the gain of electrons, a decrease in oxidation state, gain of hydrogen, or loss of oxygen. In option C, Mercury (Hg) in mercuric oxide (HgO) has an oxidation state of +2. In the product, elemental mercury (Hg) has an oxidation state of 0. The oxidation state of Hg decreases from +2 to 0, which signifies a reduction. Also, the metal oxide is losing oxygen to form the metal, which is a characteristic of reduction processes.
Let’s look at the other options:
A) 2 Mg (s) + O₂ (g) → 2 MgO (s): Mg is oxidized (0 to +2), O₂ is reduced (0 to -2).
B) S (s) + O₂ (g) → SO₂ (g): S is oxidized (0 to +4), O₂ is reduced (0 to -2).
D) Mg (s) + S (s) → MgS (s): Mg is oxidized (0 to +2), S is reduced (0 to -2).
All listed reactions are redox reactions involving both oxidation and reduction. However, option C specifically shows the reduction of a metal cation (Hg²⁺) to its elemental form (Hg⁰) by the loss of oxygen from its compound, making it a clear example of a reduction process relative to the metal. The question asks which *one* is *a* reduction reaction, and while all involve reduction, C best exemplifies the reduction of the stated element (Hg).

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