Diseases: UPSC Previous Year Questions (Science and Technology)

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

Statement 1 is correct: PCVs protect against infections caused by Streptococcus pneumoniae, which can lead to pneumonia, meningitis, and sepsis. This is particularly important in India, where pneumococcal diseases contribute significantly to child mortality.

Statement 2 is correct: By preventing pneumococcal infections, PCVs decrease the need for antibiotics, thereby mitigating the risk of developing and spreading antibiotic-resistant bacteria.

Statement 3 is incorrect: Like other vaccines, PCVs can have mild side effects such as fever, redness at the injection site, and, in rare cases, allergic reactions. No vaccine is completely free of side effects.

Explanation

Antimicrobial Resistance (AMR) is the ability of microorganisms like bacteria, viruses, fungi, and parasites to resist the effects of antimicrobial drugs, making infections harder to treat. When microorganisms such as bacteria develop resistance to multiple drugs, it is specifically termed Multidrug Resistance (MDR), posing a serious challenge to effective treatment.

Statement 1 is incorrect: Multi-drug resistance is primarily a result of microbial adaptation, excessive antibiotic use, and misuse rather than human genetic predisposition. Genetic predisposition is a genetic trait that, in response to environmental factors, may influence the potential phenotypic development of an individual organism within a species or community. Antibiotic resistance is not related to the genetic tendency of a small minority of persons in a society.

Statement 2 is correct: Misuse of antibiotics, such as incorrect dosing, premature discontinuation of prescribed antibiotics, or self-medication, allows bacteria to survive and develop resistance. WHO mentions inappropriate use of antibiotics as a major driver of antimicrobial resistance.

Statement 3 is correct: The extensive use of antibiotics in animals, especially for growth promotion and disease prevention, contributes to the development of resistant bacteria. These resistant strains can transfer to humans through the food chain or direct contact.

Statement 4 is incorrect: While having multiple chronic diseases (like diabetes, hypertension, or cancer) may lead to prolonged or frequent use of antibiotics due to recurrent infections, it is not a direct cause of multi-drug resistance (MDR) in microbial pathogens.

Explanation

The Cas9 protein, often referred to as "molecular scissors," is an enzyme utilized in targeted gene editing. It originates from the CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) system, which serves as an adaptive immune mechanism in bacteria. Guided by a specific RNA sequence, Cas9 binds to a complementary DNA sequence and introduces a double-stranded break. This break facilitates targeted modifications, such as gene insertion, deletion, or correction. Cas9 has revolutionized genetic research and therapy by enabling precise edits in the genomes of various organisms, including plants, animals, and humans. This technology holds potential for treating genetic disorders, developing disease-resistant crops, and advancing gene therapy.

Explanation

Hepatitis is an inflammation of the liver, often caused by viral infections (hepatitis A, B, C, D, E). Its symptoms include fatigue, jaundice, and abdominal pain. Statement (a) is correct: Both Hepatitis B virus (HBV) and HIV are transmitted through contact with infected blood, semen, or other body fluids. Statement (b) is incorrect: A vaccine is available for Hepatitis B, which is effective in preventing HBV infection. However there is currently no vaccine for Hepatitis C. Statement (c) is correct: The global prevalence of HBV and HCV infections is significantly higher than that of HIV. Statement (d) is correct: Both HBV and HCV can lead to chronic infections where individuals remain asymptomatic for years, often until significant liver damage has occurred.

Explanation

Birds can act as carriers of plant pathogens. As they move through crops, pathogens may stick to their feathers, beaks, or feet, transferring them from infected plants to healthy ones. Dust particles often carry fungal spores or bacterial cells. When dust is blown by the wind, these pathogens can travel to new areas, causing infections in plants far from the original source. Rainwater, particularly during heavy downpours or storms, can facilitate the spread of pathogens. Raindrops pick up pathogens from infected plants or soil and splash them onto healthy plants, promoting disease transmission. Wind plays a significant role in transporting pathogens such as fungal spores, bacteria, or insect vectors contaminated with viruses. This mechanism allows pathogens to infect plants located far from the initial infection site.

Explanation

Pair 1 is correctly matched: Lip items like lipsticks and other cosmetics including eye shadow, blush, compact powder, shampoo, and body lotion frequently include the contaminant lead.

Pair 2 is correctly matched: In some sodas and soft drinks, the citrus flavour is sometimes prevented from breaking out by the food additive brominated vegetable oil.

Pair 3 is correctly matched: MSG is commonly added to Chinese fast food and other processed foods to enhance flavor. While it is generally recognized as safe, some individuals may experience sensitivity to MSG, leading to symptoms like headaches or nausea.

Explanation

Viruses can infect bacteria and are commonly known as bacteriophages. They attach to bacterial cells and inject their genetic material, leading to the production of new viral particles within the bacterial host. Viruses that infect fungi are termed mycoviruses. These viruses can influence the physiology and pathogenicity of their fungal hosts. Notably, studies have shown that fungi can acquire viruses and viroids from plants, indicating cross-kingdom transmission. Numerous viruses infect plants, causing a variety of diseases that can significantly impact agricultural productivity. These plant viruses can be transmitted through various means, including insect vectors, mechanical damage, and seed transmission. Ex-Tobacco Mosaic Virus (TMV), infect plants, causing diseases that affect crop yields and quality.

Explanation

Option (d) is correct: H1N1 is a subtype of the Influenza A virus which causes respiratory infections in humans and animals. It is commonly known as Swine Flu because it was originally found in pigs. The virus is a result of genetic reassortment between human, swine, and avian influenza viruses.

Option (a),(b) and (c) are incorrect:

AIDS (Acquired Immunodeficiency Syndrome) is caused by the HIV (Human Immunodeficiency Virus) and not the H1N1 virus. HIV primarily affects the immune system (CD4+ T cells) which leads to weakened immunity. Bird Flu (Avian Influenza) is caused by a different subtype of Influenza A virus, such as H5N1, H7N9, H5N8, etc. H1N1 is not responsible for Bird Flu. Dengue is a mosquito-borne viral disease caused by the Dengue virus (DENV), which is transmitted by the Aedes aegypti mosquito. Dengue symptoms include high fever, severe headache, pain behind the eyes, joint pain and rash.