Biology (Part-IV) (UPSC)

Total Questions: 66

21. Aspartame is an artificial sweetener sold in the market. It consist of amino acids and provides calories like other amino acids. Yet, it is used as a low-calorie sweetening agent in food items. What is the basis of this use? [2011-1]

Correct Answer: (d) Aspartame is several times sweeter than table sugar, hence food items made with small quantities of aspartame yield fewer calories on oxidation.
Solution:Aspartame is metabolized by the body into two constituent amino acids and methanol. These hydrolysis products are handled by the body in the same way as aspartic acid. L-Phenylanine and methanol from other consumed foods. These components yield no calorie and add nothing new to the diet.

22. At present, scientists can determine the arrangement or relative positions of genes or DNA sequences on a chromosome. How does this knowledge benefit us? [2011-11]

1. It is possible to know the pedigree of livestock.
2. It is possible to understand the causes of all human diseases.
3. It is possible to develop disease-resistant animal breeds.
Which of the statements given above is/are correct ?

Correct Answer: (c) 1 and 3 only
Solution:Scientists can use sequence information to determine which genes and regulatory instructions are contained in the DNA molecule. The DNA sequence can be screened for characteristic features of genes, such as open reading frames (ORFs) and CpG islands. Homologous DNA sequences from different organisms can be compared for evolutionary analysis between species or populations. Notably, DNA sequencing can reveal changes in a gene that may cause a disease.

Sequencing DNA means determining the order of the four chemical building blocks called "bases" - that make up the DNA molecule. The sequence tells scientists the kind of genetic information that is carried in a particular DNA segment.

23. A company marketing food products advertises that its items do not contain trans fats. What does this campaign signify to the customers ? [2011-1]

1. The food products are not made out of hydrogenated oils.

2. The food products are not made out of animal fats/oils.

3. The oils used are not likely to damage the cardiovascular health of the consumers.

Which of the statements given above is/are correct?

Correct Answer: (c) 1 and 3 only
Solution:A type of trans fat occurs naturally in the milk and body fat of ruminants (such as cattle and sheep) at a level of 2-5% of total fat. Natural trans fats, which include conjugated linoleic acid (CLA) and vaccenic acid, originate in the rumen of these animals.

24. A married couple adopted a male child. A few years later, twin boys were born to them. The blood group of the couple is AB positive and O negative. The blood group of the three sons is A positive, B positive, and O positive. The blood group of the adopted son is ? [2011-1]

Correct Answer: (a) O positive
Solution:The blood group of the parents are AB and O; the biological child's blood group may be A or B and since the boy is adopted and it is given in the question that " the blood group of the three sons are A+, B+, O+".
Human beings differ in certain aspects though it appears to be similar. Various types of grouping of blood has been done. Two such groupings – the ABO and Rh – are widely used all over the world.
ABO grouping
• ABO grouping is based on the presence or absence of two surface antigens (chemicals that can induce immune response) on the RBCs namely A and B.
• Similarly, the plasma of different individuals contain two natural antibodies (proteins produced in response to antigens).
• The distribution of antigens and antibodies into four groups of blood, A, B, AB and O are given in Table below.
• ABO blood groups are controlled by the gene I. The plasma membrane of the red blood cells has sugar polymers that protrude from its surface and the kind of sugar is controlled by the gene. The gene (I) has three alleles IA, IB and i.
• The alleles IA and IB produce a slightly different form of the sugar while allele i does not produce any sugar.
• Because humans are diploid organisms, each person possesses any two of the three gene alleles.
Rh grouping
• Another antigen, the Rh antigen similar to one present in Rhesus monkeys (hence Rh), is also observed on the surface of RBCs of majority (nearly 80 per cent) of humans. Such individuals are called Rh positive (Rh+ve) and those in whom this antigen is absent are called Rh negative (Rh-ve).
• An Rh-ve person, if exposed to Rh+ve blood, will form specific antibodies against the Rh antigens. Therefore, Rh group should also be matched before transfusions.
• A special case of Rh incompatibility (mismatching) has been observed between the Rh-ve blood of a pregnant mother with Rh+ve blood of the foetus.
• Rh antigens of the foetus do not get exposed to the Rh-ve blood of the mother in the first pregnancy as the two bloods are well separated by the placenta.

25. Regular intake of fresh fruits and vegetables is recommended in the diet since they are a good source of antioxidants. How do antioxidants help a person maintain health and promote longevity? [2012-1]

Correct Answer: (c) They neutralize the free radicals produced in the body during metabolism.
Solution:Oxidation reactions can produce free radicals. In turn, these radicals can start chain reactions. When the chain reaction occurs in a cell, it can cause damage or death. When the chain reaction occurs in a purified monomer, it produces a polymer resin, such as a plastic, a synthetic fibre, or an oil paint film.

Antioxidants terminate these chain reactions by removing free radical intermediates, and inhibit other oxidation reactions. They do this by being oxidized themselves, so antioxidants are often reducing agents such as thiols, ascorbic acid, or poly phenols.

26. Which one of the following sets of elements was primarily responsible for the origin of life on the Earth? [2012-1]

Correct Answer: (b) Carbon, Hydrogen, Nitrogen
Solution:

The most abundant elements in living organisms are Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Phosphorus (P), and Sulfur (S). These are often remembered by the acronym CHNOPS. These elements form the “backbone” and functional groups of biomolecules.

• Carbon: Unique ability to form stable bonds with itself and many other elements, creating large and complex molecular structures (organic chemistry is the study of carbon compounds).
• Hydrogen: Forms bonds with almost all elements, essential for water (the solvent of life) and organic molecules.
• Oxygen: Also highly reactive, essential for water, sugars, fats, and many other organic compounds. In the early Earth, oxygen was likely less available as a free gas in the atmosphere but present in compounds like water and oxides.
• Nitrogen: Crucial component of amino acids (the building blocks of proteins) and nitrogenous bases (components of DNA and RNA).
• Phosphorus: Essential for the backbone of DNA and RNA, and a key component of ATP (the energy currency of the cell) and phospholipids (which form cell membranes).
• Sulfur: Found in certain amino acids (like methionine and cysteine) and vitamins, important for protein structure and function.

27. Consider the following kinds of organisms: [2012-1]

Consider the following kinds of organisms:

1. Bat

2. Bee

3. Bird

Which of the above is/are pollinating agent/agents?

Correct Answer: (d) 1, 2 and 3
Solution:

• Pollination is the transfer of pollen from the male part of a plant to the female part of a plant, thus, enabling fertilisation and production of seeds, most often by an animal or by wind.
• Pollinating agents are animals such as insects, birds, bees and bats; water; wind; and even plants themselves, when self-pollination occurs within a closed flower.
• Pollination is very important as it promotes the creation of new compounds that may be valuable in food or medicine as it enhances the variety within plant species. The process leads to the development of fruits, seeds, and subsequent plants used in agriculture and for livestock feed. It also helps to maintain and promote diversity within and across native plant species.
Types of pollination
• There are two types of pollination:
• Self-pollination: this type of pollination occurs within the same flower and does not require pollinating agents.
• Cross-pollination: this type of pollination occurs between the same species of flowers but from different plants. This process requires an external pollinating agent.

28. Improper handling and storage of cereal grains and oilseeds result in the production of toxins known as aflatoxins which are not generally destroyed by normal cooking process. Aflatoxins are produced by : [2013-1]

Correct Answer: (c) moulds
Solution:Aflatoxins are produced by many species of Aspergillus, a fungus. Aspergillus Flavus and Aspergillus parasiticus are weedy moulds that grow on a large number of substrates, particular under high moisture conditions.

Aflatoxin M1 is a major metabolite of aflatoxin B1 in humans and animals, which may be present in milk from animals fed with aflatoxin B1 contaminated feed.

29. Which of the following adds/add nitrogen to the soil? [2013-11]

1. Excretion of urea by animals.

2. Burning of coal by man.

3. Death of vegetation.

Select the correct answer using the codes given below.

Correct Answer: (c) 1 and 3 only
Solution:Excretion of urea by animals adds nitrogen to the soil, as urea is the main nitrogen containing substance in the urine of mammals, therefore urea is widely used in fertilizers as the convenient source of nitrogen. Death of vegetation adds up in soil organic matters including humus. As organic matters decompose inorganic nitrogen is released into the soil.

30. Which of the following diseases can be transmitted from one person to another through tattooing? [2013-11]

1. Chikungunya

2. Hepatitis B

3. HIV-AIDS

Select the correct answer using the codes given below.

Correct Answer: (b) 2 and 3 only
Solution:Body piercing or getting one's body tattooed may cost one a huge price- Infection of Hepatitis B and C virus is absolutely possible.

The needle used in the act may just be infected with the said virus causing liver disease, which in its ultimate stage often turns cancerous. This is deemed to happen if the needle is not properly sterilized.