Q. Water can dissolve more substances than any other liquid because.

(a) It is dipolar in nature.
(b) It is a good conductor of heat
(c) It has high value of specific heat
(d) It is an oxide of hydrogen

Answer: (a) It is dipolar in nature.

Water
  • A substance that displaces most compounds is known as a universal solvent. Water is known as the universal solvent because, while not complete, it can dissolve more compounds than any other solvent.
  • Molecules that have partially charged positive and negative areas are polar. Because of its polar nature, which gives each molecule a hydrophobic (fear of water) and hydrophilic (love of water) side, water dissolves more compounds than any other solvent, as is known. The oxygen atom carries a tiny negative electrical charge, whereas the side of the molecules with two hydrogen atoms carries a slight positive electrical charge.
  • Water’s polarization makes it possible for it to draw in a wide variety of molecules. Water can split the substance into its ions due to the strong attraction to ionic molecules like sodium chloride or common salt. Other molecules, like sucrose or sugar, don’t break up into ions, instead, they spread out evenly in the water.

Q. With reference to street lighting, how do sodium lamps differ from LED lamps?

  1. Sodium lamps produce light at 360 degrees but it is not so in the case of LED lamps.
  2. As street lights, sodium lamps have a longer life span than LED lamps.
  3. The spectrum of visible light from sodium lamps is almost monochromatic while LED lamps offer significant colour advantages in street lighting.

Select the correct answer using the code given below.

(a) 3 only
(b) 2 only
(c) 1 and 3 only
(d) 1, 2 and 3

Answer: (c) 1 and 3 only

Sodium Lamps
  • A sodium-vapor lamp is a gas-discharge lamp that uses sodium in an excited state to produce light at a characteristic wavelength near 589 nm.
  • The spectrum of visible light from sodium lamps is almost monochromatic as they are known for their warm yellow glow. 
  • As street lights, sodium lamps have on an average shorter lifespan than LED lamps.
  • Two varieties of such lamps exist: low pressure and high pressure.
  • Low-pressure sodium lamps
    • Low-pressure sodium lamps are highly efficient electrical light sources, but their yellow light restricts applications to outdoor lighting, such as street lamps, where they are widely used.
    • Low-pressure sodium lamps only give monochromatic yellow light and so inhibit color vision at night.
    • The bulb principally contains solid sodium metal inside a borosilicate glass tube that vaporizes once the lamp is turned on. During start (while the sodium is still in solid form) the lamp emits a dim reddish/pink glow. Once the metal is vaporized the emissions become the characteristic bright yellow associated with sodium vapor lamps.
    • The spectrum of visible emissions from an LPS light is actually very close together (589 and 589.6 nm, virtually monochromatic) resulting in the colors of illuminated objects being nearly indistinguishable.
    • Used in outdoor lighting of some parking areas and bridge underpasses.
  • High-pressure sodium lamps
    • High pressure sodium vapor (HPS) lights, similar to LPS lights, are a specific type of gas- discharge light (also known as a high intensity discharge, HID or arc light).
    • The principal difference between low and high pressure sodium lights is the operating pressure inside the lamp. As indicated by the name, “high” pressure sodium vapor lights operate at a higher internal pressure.
    • The arc tube is made of aluminum oxide and the sodium metal is combined with several other elements like mercury which counter-balances the yellow glow with some white to light blue emissions.
    • High-pressure sodium lamps emit a broader spectrum of light than the low-pressure lamps, but they still have poorer color rendering than other types of lamps.
    • Bulb Failure: Prone to flickering and activation failure. At the end of the bulbs’ lives, they are more susceptible to turning on and off without input until they inevitably fail entirely.
    • Lumen: Maintain their luminance for 90% of their life span, and still maintain 80% emission at the end of their life.
    • Lifespan: High Pressure Sodium lights tend to have a lifespan averaging 24,000 hours. 
    • Bulb Angle: 360-degree bulb angle
    • Efficacy: High efficacy that is easily comparable to LED lights.
LED Lamps
  • LED stands for light emitting diode. A diode is an electrical device or component with two electrodes (an anode and a cathode) through which electricity flows – characteristically in only one direction (in through the anode and out through the cathode).
  • Diodes are generally made from semi-conductive materials such as silicon or selenium – solid state substances that conduct electricity in some circumstances and not in others (e.g. at certain voltages, current levels, or light intensities). When current passes through the semiconductor material the device emits visible light. It is very much the opposite of a photovoltaic cell (a device that converts visible light into electrical current).
  • LED lights do not contain mercury, and therefore it has a very low environmental impact than incandescent bulbs. LEDs are increasingly common in street lights, parking garage lighting, walkway, and outdoor area lighting, refrigerated case lighting, modular lighting, and task lighting.
  • Color Temperature: Variety of color temperature options providing better lighting solutions including cooler lights than High Pressure Sodium counterpart.
  • CRI: Higher Color Rendering Index (CRIs) for better color vision at night.
  • On/Off: Responds instantaneously to on/off input without any delays and can produce a steady non-flicker light throughout their entire lifespan.
  • Warm-Up: LEDs have faster switching (no warm-up or cool-down period).
  • Size: LEDs can be much smaller than other lights.
  • Bulb Failure: LED lights slowly dim over time instead of flickering or turning on/off sporadically.
  • Lifespan: LEDs have an extremely long lifespan relative to every other lighting technology. New LEDs can last 50,000 to 100,000 hours or more.
    • The typical lifespan for a fluorescent bulb, by comparison, is 10-25% as long at best (roughly 10,000 hours).
  • Bulb Angle: 180-degree bulb angle to preserve light efficiency and allow for target lighting over areas.
  • Efficacy: The most efficiency lights on the market with high efficacy averaging about 50 lumens/watt.
Lamps

Q. The term “ACE2” is talked about in the context of

(a) genes introduced in the genetically modified plants
(b) development of India’s own satellite navigation system
(c) radio collars for wildlife tracking
(d) spread of viral diseases

Answer: (d) spread of viral diseases

ACE2
  • Angiotensin-converting enzyme 2 is an enzyme attached to the membrane of cells in the intestines, kidney, testis, gallbladder, and heart.
  • The angiotensin-converting enzyme-2 (ACE-2) has been identified as the receptor for the SARS-CoV-2 viral angiotensin-converting enzyme 2 (ACE2) acts as an entry point for coronavirus into the Human Body.
  • ACE2 is discussed in the context of the spread of viral disease.
  • ACE2 is a protein on the surface of many cell types. 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 – before entry and infection of cells. Hence, ACE2 acts as a cellular doorway – a receptor– for the virus that causes COVID-19.  
  • SARS-CoV-2 uses a human enzyme called ACE2 to enter into the cells of its host.
  • ACE2 lowers blood pressure in the human body and works against another enzyme known as ACE (which has the opposite effect).
  • The virus causes the levels of ACE to fall in the lungs and consequently pushes up the levels of ACE2.
  • This happens as a chain reaction and increases the levels of the molecule bradykinin in the cells, causing a bradykinin storm.
  • Bradykinin is a compound that is related to pain sensation and lowering blood pressure in the human body.
  • Bradykinin storm causes the blood vessels to expand and become leaky, leading to swelling of the surrounding tissue.

Q. Bisphenol A (BPA), a cause of concern, is a structural/key component in the manufacture of which of the following kinds of plastics?

(a) Low-density polyethylene
(b) Polycarbonate
(c) Polyethylene terephthalate
(d) Polyvinyl Chloride

Answer: (b) Polycarbonate

Bisphenol A (BPA)
  • Bisphenol A is a synthetically obtained colourless, crystalline organic compound that occurs in the solid phase belonging to the diphenylmethane group. It is soluble in organic solvents but poorly dissolves in water
  • Uses of Bisphenol A:
    • Bisphenol A (BPA) is commonly used to coat the insides of food cans, bottle tops, and water supply lines, and was once a component of baby bottles.
    • Bisphenol A (BPA) is a chemical produced in large quantities for use primarily in the production of polycarbonate plastics and epoxy resins. Specifically, it is used for packaging foods and beverages, baby bottles, thermal papers (i.e., receipts), and dental sealants.
    • BPA polycarbonate plastics are very sturdy in nature and are used to make large variants of microwave-proof utensils. 
    • It is used as a material for safety glasses, bulletproof windows and helmets.
    • It is used in many medical devices such as heart-lung machines, incubators, artificial kidneys, dental fillers, and sealants.
    • It is also used as eyewear glasses , due to their optical clarity.
  • Environmental impacts of Bisphenol A:
    • BPA can enter the environment directly through the leaching of chemicals or degradation of materials containing bisphenol A and may render the land unfertile and barren making it unsuitable for agriculture.
    • It  affects the growth and reproduction of marine life.
    • It causes endocrine effects in fish, amphibians, and reptiles.
  • Adverse effects of Bisphenol A on human health:
    • When ingested, the chemical disrupts the endocrine system by interfering with the hormones and affecting the brain and prostate gland of foetuses, infants, and children.
    • It can cause high blood pressure, diabetes and cardiovascular disease in adults.
    • BPA is a xenoestrogen and mimics estrogen present in the body, thus exhibiting hormone-like properties.
    • It can indirectly aid in the spread of vector-borne diseases in humans and animals.
Low-density polyethylene
  • Low Density Polyethylene (LDPE) is a flexible, odorless, transparent, 100% recyclable thermoplastic polymer popular in products like grocery/garbage bags, juice containers, and cling wrap.
  • Its flexibility, toughness, and corrosion resistance combined with its low-cost, high-efficiency production process make it an appealing choice for engineering applications, fueling demand for the production of millions of tons of LDPE each year.
  • Polyethylene is a thermoplastic polymer derived from petroleum composed of long chains of ethylene molecules known as monomers, which can be represented by the form (C2H4)n.
  • The most notable properties of LDPE are its toughness, its high flexibility at low temperatures, and its corrosion resistance. It has good strength relative to its density, which explains why it has widespread use in the production of small, lightweight carrying containers like plastic bags.
  • Some of the key properties of low density polyethylene include:
    • More branching in molecular structure
    • Low temperature flexibility
    • Toughness
    • Corrosion/Chemical Resistance
  • Low density polyethylene has properties that are attractive for applications in food-safe bagging, waterproof packaging, and other packaging materials.
Types of Plastic
Polycarbonate
  • Polycarbonates (PC) are a group of thermoplastic polymers containing carbonate groups in their chemical structures.
  • Polycarbonate is a tough, transparent plastic material with outstanding strength, stiffness, and impact resistance.
  • Its high strength makes it resistant to impact and fracture. It is lightweight so an excellent alternative to glass. PC is melted and forced into a mold with high pressure to give it the desired shape. It is widely used owing to its eco-friendly processing and recyclability.
  • Polycarbonate’s optical clarity makes it ideal for applications such as machine guards, signs, architectural glazing, face shields, skylights, and POP displays.
  • Polycarbonates do not have a unique resin identification code (RIC) and are identified as “Other”, 7 on the RIC list. Products made from polycarbonate can contain the precursor monomer bisphenol A (BPA).
  • Used for:
    • Indoor and outdoor signs
    • Architectural glazing—medical facilities, retail and government buildings, and transportation centers at risk from breakage and vandalism
    • POP displays and graphic holders
    • Skylights
    • Face shields
    • Machine guards, sight glasses
    • Semiconductor machinery components
    • Transparent manifolds
Polyethylene terephthalate
  • Polyethylene terephthalate (PET or PETE) is a condensation polymer of ethylene glycol and terephthalic acid.
  • It is a thermoplastic synthetic substance, malleable under heat, and can be placed into nearly any shape known mostly for its short PET form.
  • PET is a strong, stiff synthetic fibre and resin and a member of the polyester family of polymers. PET is spun into fibres for permanent-press fabrics and blow-molded into disposable beverage bottles.
  • Polyethylene terephthalate (PET) is very moisture tolerant. Polyethylene terephthalate has outstanding chemical resistance to organic matter and water, it is not biodegradable.
  • A list of uses of polyethylene terephthalate is given below.
    • For the manufacturing of shopping bags, water bottles, videotapes, containers and bags, clothes and housing material, water bottles, microwave containers, packaging films, etc.
    • Polyester for fabrics is strong and flexible, and when combined with materials like cotton can reduce wrinkling, and shrinking, and makes the fabric more resistant to tears.
  • Advantages of Polyethylene terephthalate
    • It is readily available and relatively inexpensive.
    • It has a high strength-to-weight ratio.
    • It is very resistant to moisture.
    • It has excellent chemical resistance to organic material and water (it is not biodegradable which is good and bad depending on your perspective and its intended use).
    • It is virtually shatterproof (it won’t break like glass packaging).
    • It is easily recycled.
    • It can be reused by conducting a series of washing processes or broken down into its constituent raw materials which can then be turned into the original resin.
    • It is highly transparent.
  • PET consists only of carbon, hydrogen, and oxygen, so if it is burned in the air (or in pure oxygen), the combustion products will be carbon dioxide and water.
Polyvinyl Chloride
  • Polyvinyl chloride is the world’s third-most widely produced synthetic polymer of plastic (after polyethylene and polypropylene).
  • Polyvinyl chloride or vinyl (PVC) is a polymer in which more than half of the content by weight consists of chlorine.
  • PVC is produced by polymerization of the vinyl chloride monomer. PVC comes in two basic forms: Rigid (sometimes abbreviated as RPVC) and flexible.
  • Resin is the main component in the production of PVC. It is white, brittle solid material available in powder form or granules. PVC is now replacing traditional constructional materials like ceramics, metal, concrete, wood, rubber and many more. PVC is produced by the process of polymerization of the vinyl chloride monomer.
  • PVC is amorphous in nature, and hence it is easily combined with other chemicals/substances. Depending on additives used in manufacturing with PVC, many qualities can be imbued in products including anti-mist, different colours, elasticity, fire retarding, flexibility, impact resistance and microbe prevention.
  • Properties of PVC:
    • By nature, PVC is a lightweight, sturdy and abrasion-resistant material.
    • This versatile thermoplastic polymer is resistant to the action of all inorganic chemicals.
    • PVC is an excellent material for insulation due to its high dielectric strength and vapour barrier capacity.
    • It can withstand extreme climatic conditions, shock and is free from corrosion. Hence, it is the preferred method for several outdoor applications.
    • Since the durability is more, long-life is assured.
    • PVC products are self-extinguishing due to high chlorine content.
    • PVC can be made more flexible and softer by adding plasticizers such as phthalate and can be bent as per requirement.
    • PVC is an intrinsic flame retardant.
    • It offers good tensile strength and is rigid by nature.
    • It is economical and is an affordable solution.
    • It demands less maintenance and offers resistance to grease and oil.
  • Applications:
    • Plasticized PVC is used in flooring or (PVC-U) unplasticized PVC is used in making window frames.
    • It is used in making sewage pipes and other pipe applications where cost or vulnerability to corrosion limit the use of metal.
    • Used in construction fields for insulation on electrical wires or in flooring for hospitals, schools, homes, and other areas where a sterile environment is a priority.
    • It is used in various industries like building, electronics, electrical, automotive, medical and packaging.
    • PVC fabric is used in the manufacture of aprons shower curtains, raincoats, jackets and sports bags.
    • It is used in the garden hose and imitation leather upholstery.

Q. “Triclosan” considered harmful when exposed to high levels for a long time, is most likely present in which of the following?

(a) Food preservatives
(b) Fruit ripening substances
(c) reused plastic containers
(d) Toiletries

Answer: (d) Toiletries

​Triclosan
  • It is an antibacterial and anti-fungal agent that slows or stops the growth of germs such as bacteria and mildew.
  • It 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, toothpaste, and some cosmetics. Therefore, Triclosan is most likely present in toiletries.
  • Triclosan is a broad-spectrum antimicrobial agent that is frequently used in pharmaceuticals and personal care products. When one uses a product containing triclosan, one can absorb a small amount through one’s skin or mouth. 
  • Triclosan added to toothpaste has been shown to help prevent gingivitis. Gingivitis is a common and mild form of gum disease that causes irritation, redness, and swelling (inflammation) of the gingiva, the part of the gum around the base of teeth.
  • 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, thus making triclosan an endocrine disruptor.
  • Endocrine disruptors are chemicals that may interfere with the body’s endocrine system and produce adverse developmental, reproductive, neurological, and immune effects in both humans and wildlife.
  • Some other studies have raised the possibility that exposure to triclosan contributes to making bacteria resistant to antibiotics.
  • Laboratory studies have demonstrated that triclosan may have the potential to adversely affect bone mineral density in cell lines or animals.
  • Also, there is still no evidence that triclosan in consumer antibacterial soaps and body washes provides any benefit over washing with regular soap and water.
Superbugs
  • Superbugs are strains of bacteria, viruses, parasites and fungi that are resistant to most of the antibiotics and other medications commonly used to treat the infections they cause.
  • A few examples of superbugs include resistant bacteria that can cause pneumonia, urinary tract infections and skin infections.
  • Antimicrobial Resistance (AMR) is the ability of a microorganism (like bacteria, viruses, and some parasites) to stop an antimicrobial drug (such as antibiotics, antivirals and antimalarials) from working against it. As a result, standard treatments become ineffective, infections persist and may spread to others.
  • Drug resistance (antimicrobial resistance) is a naturally occurring phenomenon that can be slowed, but not stopped. Over time, germs such as bacteria, viruses, parasites and fungi adapt to the drugs that are designed to kill them and change to ensure their survival. This makes previously standard treatments for some infections less effective, and sometimes ineffective. Researchers continue to evaluate how these germs develop resistance. They also study how to diagnose, treat and prevent antimicrobial resistance.
  • A superbug can infect anyone, but some people may have a higher risk for infection because they’ve been exposed to superbugs in a medical facility or have a weakened immune system because of a chronic illness.
  • Certain actions may step up the appearance and spread of antimicrobial-resistant germs, such as:
    • Using or misusing antibiotics
    • Having poor infection prevention and control practices
    • Living or working in unclean conditions
    • Mishandling food

Q. Which one of the following is a reason why astronomical distances are measured in light-years?

(a) Distance among stellar bodies do not change
(b) Gravity of stellar bodies does not change
(c) Light always travels in straight line
(d) Speed of light is always same

Answer: (d) Speed of light is always same

Light Year
  • A light-year is a measurement of distance in space. Light-year is the distance light travels in one year. The astronomical distances are measured in light-years because, the speed of light is constant throughout the universe and is known to high precision.
    • Light zips through interstellar space at 186,000 miles (300,000 kilometers) per second and 5.88 trillion miles (9.46 trillion kilometers) per year.
      • In a vacuum, light travels at 670,616,629 mph (1,079,252,849 km/h). To find the distance of a light-year, you multiply this speed by the number of hours in a year (8,766). The result: One light-year equals 5,878,625,370,000 miles (9.5 trillion km).
      • At first glance, this may seem like an extreme distance, but the enormous scale of the universe dwarfs this length.  
  • Measuring in light-years also allows astronomers to determine how far back in time they are viewing. Because light takes time to travel to our eyes, everything we view in the night sky has already happened. In other words, when you observe something 1 light-year away, you see it as it appeared exactly one year ago. 

Q. With reference to recent developments regarding ‘Recombinant vector Vaccines’, consider the following statements:

  1. Genetic engineering is applied in the development of these vaccines.
  2. Bacteria and viruses are used as vectors.

Which of the statements given above is/are correct?

(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2

Answer: (c) Both 1 and 2

Recombinant Vector Vaccines
  • Genetic engineering is applied in the development of Recombinant vector vaccines. Genetic engineering involves techniques to alter the chemistry of genetic material (DNA and RNA), to introduce these into host organisms and thus change the phenotype of the host organism. 
  • The techniques of genetic engineering include creation of recombinant DNA, use of gene cloning and gene transfer. Recombinant vaccines are made of a viral or bacterial vector. 
  • Recombinant vector vaccines are live replicating viruses that are engineered to carry extra genes derived from a pathogen—and these extra genes produce proteins against which we want to generate immunity.
  • These vaccine genomes may evolve to lose the extra genes during the process of manufacture of the vaccine or during replication within an individual, and there is a concern that this evolution might severely limit the vaccine’s efficacy.
DNA Vaccine
  • A DNA vaccine is a type of vaccine that transfects a specific antigen-coding DNA sequence into the cells of an organism as a mechanism to induce an immune response.
  • DNA vaccines work by injecting genetically engineered plasmid containing the DNA sequence encoding the antigen(s) against which an immune response is sought, so the cells directly produce the antigen, thus causing a protective immunological response.
  • The DNA is injected directly into the body’s cells, where it instructs the cells to produce the antigen.
    • The immune system then recognizes the antigen as foreign and mounts an immune response against it, which helps to develop immunity to the pathogen.
  • DNA vaccines are third-generation vaccines.
  • DNA vaccines have theoretical advantages over conventional vaccines, including the “ability to induce a wider range of types of immune response”.
  • These vaccines are yet not completely appropriate for human use and can only be used for animal species.
  • Advantages of DNA Vaccine:
    • The immune response focused on the antigen of interest
    • Cost-effective
    • Less risk for infection
    • Antigen presentation by MHC class I and class II molecules
    • Long-term persistence of immunogen
  • Limitations of DNA Vaccine:
    • Risk of affecting genes controlling cell growth
    • Possibility of tolerance to the antigen
    • Potential for atypical processing of bacterial and parasite proteins
    • Limited to protein immunogens
  • In August 2021, Indian authorities gave emergency approval to ZyCoV-D. Developed by Cadila Healthcare, it is the first DNA vaccine approved for humans.

Q. In the context of hereditary diseases, consider the following statements:

  1. Passing on mitochondrial diseases from parent to child can be prevented by mitochondrial replacement therapy either before or after in vitro fertilization of the egg.
  2. A child inherits mitochondrial diseases entirely from the mother and not from the father.

Which of the statements given above is’/are correct?

(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2

Answer: (c) Both 1 and 2

Mitochondrial diseases
  • Mitochondrial disease is a group of disorders caused by mitochondrial dysfunction.
    • Mitochondria are the organelles that generate energy for the cell and are found in every cell of the human body except red blood cells. They convert the energy of food molecules into the ATP that powers most cell functions.
    • When the number or function of mitochondria in the cell are disrupted, less energy is produced and organ dysfunction results.
  • Mitochondrial diseases take on unique characteristics both because of the way the diseases are often inherited and because mitochondria are so critical to cell function.
    • A subclass of these diseases that have neuromuscular symptoms are known as mitochondrial myopathies.
  • Mitochondria are the organelle which contain DNA in circular form, and in animals it is the only organelle in addition to nucleus which contain DNA and gene. The sperm contains very low number of mitochondria and mitochondrial gene. So, in the offspring the mitochondrial genes are inherited from the mother. Thus, a father with mitochondrial gene defect cannot transmit the disease to his offspring. 
  • Mitochondrial replacement therapy (MRT) is a form of reproductive invitro fertilization (IVF) which works on the principle of replacing a women’s mitochondrial DNA (mt-DNA) with the donor’s healthy one. The carrier mother’s pronucleus is inserted into the donor mother’s enucleated oocyte containing normal mtDNA, and the embryo is implanted into the carrier mother by IVF.
    • Mitochondrial replacement therapy can be done either before or after in vitro fertilization.
    • MRT include different techniques like spindles transfer (ST), pronuclear transfer (PNT) or polar body transfer (PBT).   
      • Pronuclear transfer technique is a significant approach of MRT administered after fertilization, in which two zygotes are raised in vitro.  
      • Maternal spindle transfer (MST) technique is executed before fertilization is a form of selective reproduction similar to prenatal diagnosis and pre-implantation genetic diagnosis (PGD).
  • The mitochondrial replacement approach is generic; instead of targeting a specific mutation, MRTs replace nearly all mitochondria and their resident mtDNA and so could be applied to any inherited
    mtDNA disease.
Genetic disorder (Hereditary diseases)
  • Hereditary diseases, also known as inherited diseases or genetic disorders is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosomal abnormality.
    • Although polygenic disorders are the most common, the term is mostly used when discussing disorders with a single genetic cause, either in a gene or chromosome.
    • These diseases are then transmitted from generation to generation, or in other words, they are inherited from parents to their children.
  • The mutation responsible can occur spontaneously before embryonic development, or it can be inherited from two parents who are carriers of a faulty gene (autosomal recessive inheritance) or from a parent with the disorder (autosomal dominant inheritance).
  • When the genetic disorder is inherited from one or both parents, it is also classified as a hereditary disease. Some disorders are caused by a mutation on the X chromosome and have X-linked inheritance. Very few disorders are inherited on the Y chromosome or mitochondrial DNA (due to their size).
  • Genetic disorders are present before birth, and some genetic disorders produce birth defects, but birth defects can also be developmental rather than hereditary.
    • The opposite of a hereditary disease is an acquired disease. Most cancers, although they involve genetic mutations to a small proportion of cells in the body, are acquired diseases. Some cancer syndromes, however, such as BRCA mutations, are hereditary genetic disorders.
  • Most common hereditary diseases:
    • Skin cancer
    • Cardiomyopathies (hypertrophic cardiomyopathy, dilated cardiomyopathy, arrhythmogenic cardiomyopathy and restrictive cardiomyopathy)
    • arthritis
    • Inherited arrhythmia syndromes (sudden arrhythmic death syndrome, or SADS), long QT syndrome, Brugada, Catecholamainergic polymorphic ventricular tachycardia (CPTV).
    • Inherited aortopathies, for example Marfan syndrome
    • Breast cancer
    • Prostate cancer
    • Lung cancer
    • Neuromuscular disorders (eg muscular dystrophy, myotonic dystrophy)
    • Familial hypercholesterolaemia
hereditary diseases

Q. Bollgard I and Bollgard II technologies are mentioned in the context of

(a) Clonal propagation of crop plants
(b) Developing genetically modified crop plants
(c) Production of plant growth substances
(d) Production of biofertilizers

Answer: (b) Developing genetically modified crop plants

Bollgard I and Bollgard II technologies:
  • Bollgard I Bt cotton (single-gene technology) is India’s 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 (GEAC), the Indian regulatory body for biotech crops.
    • Bollgard I cotton provides in-built protection for cotton against destructive American Bollworm Heliothis Armigera infestations and contains an insecticidal protein from a naturally occurring soil microorganism, Bacillus thuringiensis (Bt).
    • Bollgard II technology contains a superior double-gene technology – Cry1Ac and Cry 2Ab which provides protection against bollworms and Spodoptera caterpillar, leading to better boll retention, maximum yield, lower pesticides costs, and protection against insect resistance.
    • Both, Bollgard II and Bollgard I insect-protected cotton is widely planted around the world as an environmentally friendly way of controlling bollworms.
  • BT Cotton:
    • In order to tackle the bollworm attack that had devastated cotton crops in the past, Bt cotton was introduced which was jointly developed by the Maharashtra Hybrid Seeds Company (Mahyco) and the US seed company Monsanto.
    • In 2002, the GEAC approved Bt Cotton for commercial cultivation in 6 states such as Andhra Pradesh, Gujarat, Karnataka, Madhya Pradesh, Maharashtra, and Tamil Nadu. It has to be noted that, Bt cotton is the first and only transgenic crop approved by the GEAC.
Genetically Modified (GM) Crops
  • GM crops are derived from plants whose genes are artificially modified, usually by inserting genetic material from another organism, in order to give it new properties, such as increased yield, tolerance to a herbicide, resistance to disease or drought, or improved nutritional value.
  • Probably the best-known variety of GM rice is golden rice.
    • Golden rice involves the insertion of genes from a plant – both daffodils and maize have been used – and a soil bacterium to create a grain that is enriched with Vitamin A.
  • Earlier, India approved the commercial cultivation of only one GM crop, Bt cotton, but GEAC has recommended GM Mustard for commercial use.
  • Advantages:
    • Increased Yield: Genetically modified seeds dramatically increase the yield of the plant. This means that with the same plot of land, a farmer can now produce noticeably more crops.
    • Beneficial in Specific Climates: Genetically modified seeds can also be produced for specific conditions or climates. For example, drought-resistant seeds can be used in places with little water to ensure healthy crop growth.
  • Disadvantages:
    • Manipulation of Seeds Cost: Only a few companies are in charge of creating and selling modified seeds. With a near monopoly, this means that there are few choices available to those buying seeds.
    • Seeds can’t be Replanted: Genetically modified seeds do not create viable seed offspring by design. This means that every time you want to plant a new crop, you have to go to the company you originally bought the seeds from.
    • Environmental Concern: They can decrease species diversity. For example, insect-resistant plants might harm insects that are not their intended target and destroy that particular insect species.
    • Ethical Concern: GM crop is the violation of natural organisms’ intrinsic values by mixing among species.
      • There have also been concerns of mixing animal genes in plants.
GM Mustard
  • Dhara Mustard Hybrid (DMH-11) is an indigenously developed transgenic mustard. It is a genetically modified variant of Herbicide Tolerant (HT) mustard.
  • It contains two alien genes (‘barnase’ and ‘barstar’) isolated from a soil bacterium called Bacillus amyloliquefaciens that enable breeding of high-yielding commercial mustard hybrids.
  • It has been developed by the Centre for Genetic Manipulation of Crop Plants (CGMCP) at Delhi University.
  • Significance: India produces only 8.5-9 million tonnes (mt) of edible oil annually while it imports 14-14.5 mt which entailed a record foreign exchange outgo of USD 18.99 billion in the fiscal year ended March 31, 2022. Further, GM mustard would make India self-reliant in oil production and help in saving forex.
    • Mustard varieties in India have a narrow genetic base. The barnase-barstar system enables breeding of hybrids from a wider range of mustards, including those of East European origin such as ‘Heera’ and ‘Donskaja’.

Q. In a pressure cooker, the temperature at which the food is cooked depends mainly upon which of the following?

  1. Area of the hole in the lid
  2. Temperature of the flame
  3. Weight of the lid

Select the correct answer using the code given below.

(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1,2 and 3

Answer: (c) 1 and 3 only

Notes:
  • Area of the hole in the lid:
    • The hole in the lid of the pressure cooker is primarily for the steam vent or whistle. The size of the hole will determine how much pressure can be built up inside the cooker before steam starts venting. A larger hole might let out steam more quickly, preventing as high a pressure from building up, whereas a smaller hole would let the pressure build more. The pressure inside the cooker determines the boiling point of water inside, which, in turn, affects the temperature at which the food cooks.
  • Temperature of the flame:
    • The temperature of the flame will determine how quickly the water inside the pressure cooker boils and thus how quickly the pressure builds up. However, once the desired pressure is reached, the temperature inside the cooker remains relatively constant, regardless of the flame’s temperature. The flame’s temperature might influence how quickly the cooker reaches its cooking temperature, but it doesn’t change the cooking temperature itself.
  • Weight of the lid:
    • The weight of the lid (or, more accurately, the weight of the pressure regulator or whistle on top of the cooker) determines the pressure inside the cooker. A heavier lid or weight will allow for a higher internal pressure before steam starts to vent, leading to a higher cooking temperature.

Q. Consider the following:

  1. Bacteria
  2. Fungi
  3. Virus

Which of the above can be cultured in an artificial/ synthetic medium?

(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1,2 and 3

Answer: (a) 1 and 2 only

Notes
  • 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.
    • Viruses lack metabolic machinery of their own and are totally dependent on their host cell for replication, they cannot be grown in synthetic culture media. 
  • Bacteria can be grown in synthetic culture media. Researchers a had rewritten the DNA of the bacteria Escherichia coli, fashioning a synthetic genome four times larger and far more complex than any previously created.  
  • Fungi can be grown in synthetic culture media. Four allergologically important fungi, viz. Aspergillus fumigatus, Alternaria Penicillium notatum, and Cladosporium herbarum, were cultured in a pure synthetic medium.  

Q. Consider the following statements:

  1. Adenoviruses have single-stranded DNA genomes whereas retroviruses have double-stranded DNA genomes.
  2. Common cold is sometimes caused by an adenovirus whereas AIDS is caused by a retrovirus.

Which of the statements given above is/are correct?

(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2

Answer: (b) 2 only

Adenoviruses:
  • ​Adenoviruses are a group of common viruses that infect the lining of your eyes, airways and lungs, intestines, urinary tract, and nervous system. They’re common causes of fever, coughs, sore throats, diarrhoea, and pink eye. Infections happen in children more often than in adults, but anyone can get them. 
  • Adenovirus is a type of virus that has no envelope whereas retroviruses are characterized as enveloped viruses.
  • Scientists use these viruses as “Viral Vectors” in making vaccines. Viral vectors are tools used to deliver genetic material into cells.
  • Adenoviruses have double-stranded DNA genomes while Retroviruses have single-stranded DNA genomes. 
  • Common cold can sometimes be caused by adenoviruses while AIDS is caused by a retrovirus. 
    • HIV is classified as a retrovirus because it contains reverse transcriptase. It is a D-type virus in the Lentivirus family.   
Retrovirus
  • Retroviruses are a type of virus in the viral family called Retroviridae. A retrovirus uses RNA as its genomic material.
  • A retrovirus is a type of virus that inserts a DNA copy of its RNA genome into the DNA of a host cell that it invades, thus changing the genome of that cell.
    • After invading a host cell’s cytoplasm, the virus uses its own reverse transcriptase enzyme to produce DNA from its RNA genome, the reverse of the usual pattern, thus retro (backwards).
    • The new DNA is then incorporated into the host cell genome by an integrase enzyme, at which point the retroviral DNA is referred to as a provirus.
    • The host cell then treats the viral DNA as part of its own genome, transcribing and translating the viral genes along with the cell’s own genes, producing the proteins required to assemble new copies of the virus.
  • Many retroviruses cause serious diseases in humans, other mammals, and birds.
retrovirus
RetrovirusVirus
These have RNA as genetic material.These have RNA and DNA as the genetic material.
They undergo reverse transcription to convert the RNA into DNA.Only RNA viruses undergo reverse transcription.