UPSC Prelims Previous Year Questions 2021: Science & Technology | Science & Technology for UPSC CSE PDF Download

Ans: (c)
Lemongrass is a tall herb that is abundantly found in tropical and sub-tropical areas of Asia, Africa and Australia. It is known to be an excellent mosquito repellant. Around 95% of mosquitos from a specific range of species are either killed or completely repelled due to the intense odour of lemongrass oil. Therefore, option (c) is the correct answer.

Ans: (c)

• Recombinant vector vaccines are made through genetic engineering. The gene that creates the protein for a bacteria or virus is isolated and placed inside another cell’s genes. Hence, statement 1 is correct.
• Numerous viral vectors are available for vaccine development, such as vaccinia, modified vaccinia virus Ankara, adenovirus, adeno-associated virus, retrovirus/lentivirus, alphavirus, herpes virus, etc. Hence, statement 2 is correct. Therefore, option (c) is the correct answer.

Ans: (c)

• The technological development allows nearly complete replacement of the cytoplasm of egg/embryo, eliminating the transmission of undesired defective mitochondria for patients with inherited mitochondrial diseases, which is called mitochondrial replacement therapy (MRT). These processes use assisted reproductive technology, including in vitro fertilization. The father’s sperm can fertilize the patient egg before the maternal genetic material is removed or after the maternal genetic material has been transferred to the donor egg. Hence, statement 1 is correct.
• Mitochondrial diseases are chronic (long-term), genetic, often inherited disorders that occur when mitochondria fail to produce enough energy for the body to function properly. As the mitochondrial genome is inherited exclusively from the mother, the child inherits mitochondrial diseases entirely from mother and not from father. Hence, statement 2 is correct.

Therefore, option (c) is the correct answer.

Ans: (b)
Bollgard I - Bt cotton (single-gene technology) is first biotech crop technology approved for commercialization in India in 2002, followed by Bollgard II - double-gene technology in mid-2006, by the Genetic Engineering Approval Committee, the Indian regulatory body for biotech crops.
Therefore, option (b) is the correct answer.

Ans: (d)

• The Charles law states that pressure (P), volume (V) and temperature (T) is equal to a constant K i.e. PVT = k.
• From the above-given equation, we can infer that temperature is dependent on pressure and volume. Pressure in the cooker depends on the area of the hole in the lid, the bigger the hole in the lid, the lesser will be the pressure inside the cooker and hence temperature will be affected. Hence, 1 is correct.
• The more is the temperature of the flame the more will be the temperature inside the cooker. Hence, 2 is correct.
• The weight of the lid has a direct connection in relation to maintaining enough pressure in the lid, heat release and heat-storing inside the cooker and hence can be linked with the temperature inside the cooker. Hence, 3 is correct.

Therefore, option (d) is the correct answer.

Ans: (a)
Bacteria and Fungi can be cultured in an artificial/synthetic medium. Whereas viruses require a living host cell for replication. Infected host cells (eukaryotic or prokaryotic) can be cultured and grown, and then the growth medium can be harvested as a source of the virus. Hence, 1 and 2 are correct and 3 is not correct.
Therefore, option (a) is the correct answer.

Ans: (b)

• Adenovirus is a type of virus that has no envelope whereas retroviruses are characterized as enveloped viruses. Adenoviruses have double-stranded linear DNA and are associated with two major core proteins. A retrovirus is a virus that uses RNA as its genetic material. When a retrovirus infects a cell, it makes a DNA copy of its genome that is inserted into the DNA of the host cell. Hence, statement 1 is not correct.
• Adenoviruses are common viruses that cause a range of illnesses. They can cause cold-like symptoms, fever, sore throat, bronchitis, pneumonia, diarrhoea, and pink eye (conjunctivitis). Whereas, retroviruses can cause several human diseases such as some forms of cancer and AIDS. Hence, statement 2 is correct.

Therefore, option (b) is the correct answer.

Ans: (a)
An important feature of the water molecule is its polar nature i.e., its polarity allows water to dissolve other polar substances very easily.
Therefore, option (a) is the correct answer.

Ans: (c)

• LEDs emit light for 180 degrees. This is typically an advantage because the light is usually desired over a target area (rather than all 360 degrees around the bulb).
• Whereas Sodium lamps emit light omnidirectionally. This means they emit light for 360 degrees, requiring fixture housings or reflectors to direct a large portion of the emissions to the desired target area. Hence, 1 is correct.
• LEDs have an extremely long lifespan relative to every other lighting technology. New LEDs can last 50,000 to 100,000 hours or more. Hence, 2 is not correct.
• Sodium lamps have the worst colour rendering of any bulb. They produce a dark yellow glow which is generally a very low-quality light. LEDs are available in a wide range of colour temperatures that generally span from 2200K-6000K (ranging from “warm” yellow to light or “cool” blue). Hence, 3 is correct.

Therefore, option (c) is the correct answer.

Ans: (d)

• ‘ACE2’ is a proteinaceous enzyme on the surface of many cell types that stands for Angiotensin Convertase Enzyme-2. It is an enzyme that generates small proteins by cutting up the larger protein angiotensinogen that then goes on to regulate functions in the cell.
• Using the spike-like protein on its surface, the SARS-CoV-2 virus binds to ACE2 like a key being inserted into a lock – prior to entry and infection of cells. Hence, ACE2 acts as a cellular doorway or a receptor for the virus that causes COVID-19.

Therefore, option (d) is the correct answer.

Ans: (b)
Bisphenol A (BPA) is a chemical produced in large quantities, primarily for the use in the production of polycarbonate plastics and epoxy resins. Therefore, option (b) is the correct answer.

Ans: (d)
Triclosan is an ingredient added to many consumer products intended to reduce or prevent bacterial contamination. It is added to toiletries like antibacterial soaps and body washes, toothpaste, and some cosmetics. Therefore, option (d) is the correct answer.

Ans: (d)

• A light-year is the distance a beam of light travels in a single Earth year, or 6 trillion miles (9.7 trillion kilometers).
• The reason for using light years to measure distance in space is because throughout the universe, light travels at exactly the same speed.

Therefore, option (d) is the correct answer.