UPSC 2021 Science and Technology Questions with Answers

Explanation

Mitochondrial diseases are a group of genetic disorders caused by dysfunction in the mitochondria, the cell’s energy-producing structures.

Statement 1 is correct: Mitochondrial Replacement Therapy (MRT) is an advanced reproductive technique designed to prevent the transmission of mitochondrial diseases from mother to child. MRT involves replacing defective mitochondria in an egg or embryo with healthy mitochondria from a donor. This can be achieved through methods such as:

Spindle Transfer: Performed before fertilization, where the nuclear DNA from the mother’s egg is transferred to a donor egg with healthy mitochondria, followed by fertilization. Pronuclear Transfer: Conducted after fertilization, where the pronuclei (genetic material) from a fertilized egg are transferred into a donor zygote that has healthy mitochondria. These techniques aim to ensure that the resulting child inherits healthy mitochondria, thereby preventing mitochondrial diseases.

Statement 2 is correct: A child inherits mitochondrial diseases entirely from the mother and not from the father. Mitochondria are unique organelles within cells that have their own DNA, known as mitochondrial DNA (mtDNA). Unlike nuclear DNA, which is inherited from both parents, mtDNA is typically inherited exclusively from the mother. This is because the mitochondria in the sperm are usually destroyed or degraded after fertilization, and thus do not contribute to the embryo’s mitochondrial pool. Consequently, if a mother has a mitochondrial disease (caused by mutations in her mtDNA), there is a risk that she can pass it on to her children, while fathers do not pass on mtDNA to their offspring, and thus do not transmit mitochondrial diseases.

Explanation

ACE2 (Angiotensin Converting Enzyme 2) is a protein on the surface of many cell types and tissues, including the lungs, heart, blood vessels, kidneys, liver, and gastrointestinal tract. It serves as the entry point for certain coronaviruses, notably SARS-CoV-2, the virus responsible for COVID-19. The virus’s spike protein binds to the ACE2 receptor, facilitating its entry into host cells and leading to infection.

Explanation

Adenoviruses are non-enveloped, double-stranded DNA viruses that infect a wide range of hosts, including humans. They are known for their ability to efficiently infect various cell types. A retrovirus is a virus that uses RNA as its genetic material. Upon infection with a retrovirus, a cell converts the retroviral RNA into DNA, which in turn is inserted into the DNA of the host.

Statement 1 is incorrect: Adenoviruses possess linear, double-stranded DNA genomes whereas retroviruses have single-stranded RNA genomes. Upon infecting a host cell, retroviruses use the enzyme reverse transcriptase to convert their RNA into double-stranded DNA, which is then integrated into the host’s genome.

Statement 2 is correct: Adenoviruses are known to cause respiratory illnesses, including symptoms similar to the common cold. AIDS (Acquired Immunodeficiency Syndrome) is caused by the Human Immunodeficiency Virus (HIV), which is a retrovirus.

Explanation

A Recombinant Vector Vaccine is a vaccine that uses a genetically modified virus or bacterium as a carrier to deliver pathogen-specific genes, triggering an immune response.

Statement 1 is correct: Recombinant vector vaccines are developed using genetic engineering to insert genes encoding antigens into harmless viruses or bacteria, which serve as vectors. These vectors deliver the genetic material into the body, enabling the expression of target antigens and triggering an immune response against the pathogen. Examples include viral vector vaccines like Oxford-AstraZeneca (ChAdOx1 nCoV-19) and Sputnik V for COVID-19.

Statement 2 is correct: Both bacteria (such as Salmonella) and viruses (such as adenoviruses and vesicular stomatitis virus) can be used as vectors to deliver genetic material into host cells to stimulate an immune response.

Explanation

Astronomical distances are measured in light-years to effectively express the vast distances in space using a consistent and universal unit. A light-year represents the distance light travels in one year in a vacuum, which is approximately 9.46 trillion kilometers (5.88 trillion miles). Astronomers calculate the distances of stars and other celestial objects in the time it takes for light to reach us since estimating distances in miles or kilometres is inadequate on the cosmological scale. Since the speed of light is known to be constant throughout the universe and for high precision, astronomical distances are expressed in terms of light-years. The fastest light can move is in vacuum.

Explanation

A pressure cooker is a sealed chamber that traps the steam generated as its contents are heated. As steam builds, pressure increases, driving the boiling point of water past 212°F (100°C). In general, this higher temperature shortens cooking times and, due to a lack of evaporation, extracts flavor more efficiently from foods.

Statement 1 is correct: The area of the hole directly influences the pressure and temperature inside the cooker. The hole in the lid is where steam escapes through the pressure regulator (weight valve). A smaller hole allows less steam to escape, which increases the pressure inside, raising the boiling point of water and increasing the cooking temperature. If the hole is larger, more steam escapes, reducing the pressure and lowering the cooking temperature.

Statement 2 is incorrect: A higher flame heats the pressure cooker faster but it does not increase the maximum cooking temperature once the cooker reaches its operating pressure. The pressure and temperature inside the cooker are controlled by the pressure regulator (weight valve), not the external flame. Once the required pressure is reached, excess heat only results in more steam escaping through the valve rather than increasing the cooking temperature.

Statement 3 is correct: The weight of the lid (specifically, the weight valve) is a key factor in determining the cooking temperature. The weight of the pressure regulator (weight valve) on the lid determines the maximum pressure inside the cooker. A heavier weight means the steam must build up more pressure before it can escape, increasing the boiling point of water and the cooking temperature. If the weight is lighter, steam escapes more easily, resulting in lower pressure and temperature inside the cooker.

Explanation

The artificial culture media, also referred to as the growth medium, is a setting for the development of many kinds of microorganisms. The agarose and nutrients needed for the microorganism’s growth are present in the culture medium. This medium is first sterilised to prevent contamination, which prevents the growth of undesirable microorganisms and ensures that it only contains the microbes of interest.

Option 1 is correct: Bacteria can be easily grown on artificial or synthetic media as these provide the necessary nutrients for their growth. These media typically include essential components like carbon, nitrogen, vitamins, and minerals. For instance, nutrient agar and broth are commonly used for culturing bacteria, and Escherichia coli can be grown on Luria-Bertani (LB) agar.

Option 2 is correct: Fungi, including yeasts and molds, can thrive on artificial media specifically formulated for their growth. Media such as Sabouraud dextrose agar and potato dextrose agar are designed to support fungal growth by providing nutrients and maintaining an acidic pH, which inhibits bacterial contamination.

Option 3 is incorrect: Viruses differ significantly from bacteria and fungi because they cannot replicate independently. Being obligate intracellular parasites they require living host cells to reproduce. Thus, they are cultured by infecting host systems such as bacterial cells (for bacteriophages) or eukaryotic cells (for animal viruses) and cannot grow on synthetic media alone.

Explanation

Statement 1 is correct: Sodium Lamps emit light omnidirectionally (360 degrees), necessitating the use of reflectors to direct light toward the desired area. LED Lamps emit light directionally (typically around 180 degrees), allowing for more efficient illumination with minimal light loss.

Statement 2 is incorrect: Sodium Lamps have a shorter operational lifespan compared to LEDs. LED Lamps offer a longer lifespan, often exceeding that of sodium lamps, leading to reduced maintenance and replacement costs.

Statement 3 is correct: Sodium Lamps produce a nearly monochromatic light, resulting in poor color rendering and making it difficult to distinguish colors under their illumination. LED Lamps provide a broad spectrum of visible light, offering superior color rendering and enhancing visibility and safety in street lighting applications.

Explanation

Bisphenol A (BPA) is an industrial chemical primarily used in the production of polycarbonate plastics and epoxy resins. Polycarbonate plastics are known for their durability and clarity and are commonly utilized in items such as water bottles, food storage containers, and eyewear. It has been identified as an endocrine disruptor, meaning it can interfere with the body’s hormonal systems. Research has linked BPA exposure to various health issues, including reproductive disorders, metabolic disease, and developmental problems in children. Due to these concerns, many regulatory agencies have evaluated the safety of BPA in consumer products.

Explanation

Triclosan is an ingredient added to many consumer products intended to reduce or prevent bacterial contamination. It is added to some antibacterial soaps and body washes, toiletries, toothpastes, and some cosmetics. Some short-term animal studies have shown that exposure to high doses of triclosan is associated with a decrease in the levels of some thyroid hormones. Other studies have raised the possibility that exposure to triclosan contributes to making bacteria resistant to antibiotics.