Science and Technology: UPSC Previous Year Questions (Prelims)

Explanation

Option (a) is correct: The average fat content of buffalo milk is approximately 7.2%, significantly higher than that of cow>s milk. Buffalo milk is richer in fat compared to cow>s milk, which typically contains around 3-4% fat. The higher fat content in buffalo milk contributes to its creamy texture and makes it ideal for producing dairy products like butter, ghee, and cheese. Options (b), (c), and (d) are incorrect: 4.5% is typical of cow’s milk, while 9.0% and 10.0% are not average values for buffalo milk.

Explanation

Option (d) is correct: Fructose is the major component of honey making up about 38-40% of its composition. It is a monosaccharide and is sweeter than glucose. The high fructose content is responsible for honey>s sweetness and its resistance to crystallization compared to glucose. Options (a), (b), and (c) are incorrect:

Glucose is one of the primary sugars found in honey, but it is not the major component. Honey typically contains about 30-35% glucose. Glucose is a monosaccharide and contributes to the sweetness and crystallization of honey. Sucrose is a disaccharide composed of glucose and fructose. While it is present in honey, it is found in very small amounts (usually less than 5%). Most of the sucrose in nectar is broken down into glucose and fructose by enzymes during the honey-making process. Maltose is not a significant sugar in honey. It is also known as maltobiose or malt sugar which is a disaccharide formed from two units of glucose joined with an -bond between the glucose units.

Explanation

Option (c) is correct: Coronary arteries are responsible for supplying oxygen-rich blood to the heart muscle. They ensure the heart gets the necessary oxygen and nutrients for its functioning. Options (a), (b), and (d) are incorrect:

The carotid arteries are major blood vessels in the neck that supply oxygenated blood to the brain, face, and neck. The hepatic arteries supply oxygenated blood to the liver along with the hepatic portal vein. The pulmonary arteries carry deoxygenated blood from the heart to the lungs for oxygenation.

Explanation

Option (d) is correct: The recommended dietary allowance (RDA) of protein for a moderately active woman is 46 grams per day. This value is based on the average need for maintaining health, muscle repair, and proper physiological functioning. The Recommended Dietary Allowance (RDA) for protein is a modest 0.8 grams of protein per kilogram of body weight. Options (a), (b), and (c) are incorrect: 30 g, 37 g, and 40 g are below the daily requirement for a moderately active woman.

Explanation

A is matched with 5: Malaria is caused by the Plasmodium parasite which infects red blood cells. The parasite multiplies in the blood leading to symptoms such as fever, chills, and anemia. B is matched with 4: Filaria, or lymphatic filariasis is caused by parasitic worms (Wuchereria bancrofti, Brugia malayi, etc.) that infect the lymphatic system including lymph nodes. This leads to swelling and conditions like elephantiasis. C is matched with 2: Encephalitis is an inflammation of the brain which is often caused by viral infections (e.g., herpes simplex virus, Japanese encephalitis virus). It affects brain tissue and can lead to neurological symptoms. D is matched with 1: Leukaemia is a type of cancer that affects the bone marrow and blood. It involves the overproduction of abnormal white blood cells which disrupts normal blood cell production.

Explanation

An antigen is any substance (e.g., proteins, polysaccharides, or toxins) that the immune system recognizes as foreign. When an antigen enters the body, it triggers an immune response leading to the production of antibodies and activation of immune cells like T-cells and B-cells. Options (a), (b), and (d) are incorrect:

Antigens do not have a role in regulating body temperature. Lowering body temperature is typically associated with antipyretics (e.g., paracetamol) or the body>s response to infections (fever reduction). Antigens do not destroy harmful bacteria. Instead they are recognized by the immune system which then activates immune responses (e.g., antibodies, white blood cells) to neutralize or destroy pathogens like bacteria. Antigens are not used as antidotes to poison. Antidotes are specific substances (e.g., activated charcoal, atropine) that neutralize or counteract the effects of toxins or poisons.

Explanation

The genome of yeast (Saccharomyces cerevisiae) was the first eukaryotic genome to be fully sequenced. The sequencing was completed in 1996 which marked a major milestone in genomics.

Explanation

DNA damage and permanent mutations are likely in professionals exposed to mutagenic agents like radiation, toxic chemicals, or hazardous environments.

Statement 1 is correct: Researchers using Carbon-14 isotopes are exposed to beta radiation from the radioactive isotope. Prolonged exposure can damage DNA and increase the risk of mutations.

Statement 2 is correct: X-ray technicians are at risk due to ionizing radiation, which can break DNA strands and cause chromosomal abnormalities. Protective measures like lead aprons are essential to minimize exposure.

Statement 3 is incorrect: While coal miners are exposed to harmful substances like coal dust and radon gas, these hazards are more strongly linked to respiratory diseases (e.g., black lung disease) and lung cancer, rather than direct, widespread DNA changes. Hence, it may not be included as a primary factor for widespread DNA changes.

Statement 4 is correct: Chemicals found in dyes and paints, such as benzene and lead-based compounds, can be harmful. They can cause cell damage and increase the risk of DNA changes. Long-term exposure is linked to a higher risk of cancer.

Explanation

Total internal reflection occurs when light travels from a medium with a higher refractive index to a medium with a lower refractive index, and the angle of incidence exceeds the critical angle. From the given options, total internal reflection can take place when light travels from Diamond to glass. This is because diamond has a higher refractive index than glass, so when light travels from diamond to glass, it can undergo total internal reflection if the angle of incidence is greater than the critical angle.

Explanation

Assertion (A) is true: A transformer is designed to change the voltage level of an alternating current (AC) by using electromagnetic induction, either increasing (stepping up) or decreasing (stepping down) the voltage. Reason (R) is false: A transformer only works with alternating current (AC) because it relies on the changing magnetic field created by the alternating current to induce voltage in the secondary coil. It does not function with direct current (DC).