12 sample questions are shown here; sign up free to practise all 80.
Q1Science·Cell Biology and GeneticsPYQ 2025
Consider the following statements:
1. No virus can survive in ocean waters.
2. No virus can infect bacteria.
3. No virus can change the cellular transcriptional activity in host cells.
Which of the statements given above are correct?
- AOnly one
- BOnly two
- CAll three
- DNoneCorrect
Explanation
Correct. Marine viruses (bacteriophages) thrive in oceans; bacteriophages specifically infect bacteria; and many viruses alter host cell transcription by hijacking cellular machinery.
Why the other options are incorrect
- Option A
All three statements are incorrect, so saying only one is correct is wrong.
- Option B
All three statements are factually false, not just two.
- Option C
All three statements are false, not correct.
Q2Science·Cell Biology and GeneticsPYQ 2022
Which one of the following statements best describes the role of B cells and T cells in the human body?
- AThey protect the body from environmental allergens.
- BThey alleviate the body's pain and inflammation.
- CThey act as immunosuppressants in the body.
- DThey protect the body from diseases caused by pathogens.Correct
Explanation
Correct. B cells produce antibodies (humoral immunity) and T cells destroy infected cells (cell-mediated immunity), together forming the adaptive immune defence against pathogens.
Why the other options are incorrect
- Option A
B cells and T cells are part of adaptive immunity against pathogens, not specifically designed to counter environmental allergens.
- Option B
Pain and inflammation relief is managed by anti-inflammatory mediators and analgesics, not the primary role of B and T lymphocytes.
- Option C
B and T cells activate the immune response rather than suppress it; immunosuppression is the opposite of their function.
Q3Science·Cell Biology and GeneticsPYQ 2021
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?
- A1 only
- B2 onlyCorrect
- CBoth 1 and 2
- DNeither 1 nor 2
Explanation
Correct. Adenoviruses can cause common cold and HIV (a retrovirus) causes AIDS. However, statement 1 is wrong because adenoviruses have dsDNA and retroviruses have ssRNA genomes.
Why the other options are incorrect
- Option A
Statement 1 is incorrect because adenoviruses have double-stranded DNA genomes and retroviruses have single-stranded RNA genomes, not the other way around.
- Option C
Statement 1 reverses the genome types; adenoviruses have dsDNA and retroviruses carry ssRNA, so only statement 2 is correct.
- Option D
Statement 2 is factually correct since adenoviruses do cause some common colds and HIV is a retrovirus.
Q4Science·Cell Biology and GeneticsPYQ 2020
Which of the following statements are correct regarding the general difference between plant and animal cells?
1. Plant cells have cellulose cell walls whilst animal cells do not.
2. Plant cells do not have plasma membranes unlike animal cells which do.
3. Mature plant cell has one large vacuole whilst an animal cell has many small vacuoles.
Select the correct answer using the code given below:
- A1 and 2 only
- B2 and 3 only
- C1 and 3 onlyCorrect
- D1, 2 and 3
Explanation
Correct. Plant cells have rigid cellulose cell walls absent in animal cells, and mature plant cells typically have a single large central vacuole compared to multiple small vacuoles in animal cells. Both cell types have plasma membranes.
Why the other options are incorrect
- Option A
Statement 2 is incorrect because both plant and animal cells possess plasma membranes; the cell wall in plants is an additional outer layer.
- Option B
Statement 2 is wrong; plant cells do have plasma membranes beneath their cell walls.
- Option D
Statement 2 is false because plant cells have plasma membranes just like animal cells.
Q5Science·Cell Biology and GeneticsPYQ 2019
Which of the following are the reasons for the occurrence of multi-drug resistance in microbial pathogens in India?
1. Genetic predisposition of some people
2. Taking incorrect doses of antibiotics to cure diseases
3. Using antibiotics in livestock farming
4. Multiple chronic diseases in some people
Select the correct answer using the code given below.
- A1 and 2
- B2 and 3 onlyCorrect
- C1, 3 and 4
- D2, 3 and 4
Explanation
Correct. Incorrect antibiotic dosing creates selective pressure favouring resistant strains, and widespread antibiotic use in livestock farming accelerates resistance gene spread in microbial populations.
Why the other options are incorrect
- Option A
Genetic predisposition of humans does not cause multi-drug resistance in microbes; resistance arises from selective pressure due to antibiotic misuse.
- Option C
Neither genetic predisposition nor chronic diseases in humans directly cause drug resistance in microbes.
- Option D
Chronic diseases in patients do not cause microbial drug resistance; resistance is driven by antibiotic misuse and overuse.
Q6Science·Cell Biology and GeneticsPYQ 2013
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:
- ABacteria
- BProtozoa
- CMouldsCorrect
- DViruses
Explanation
Correct. Aflatoxins are produced by moulds of the genus Aspergillus (mainly A. flavus and A. parasiticus) that contaminate improperly stored grains and oilseeds.
Why the other options are incorrect
- Option A
Bacteria produce various toxins but aflatoxins are specifically produced by fungal species, not bacteria.
- Option B
Protozoa are unicellular organisms that cause infections but are not known to produce aflatoxins.
- Option D
Viruses are obligate intracellular parasites that do not produce metabolic toxins like aflatoxins.
Q7Science·Cell Biology and GeneticsPYQ 2013
With reference to the usefulness of the by-products of sugar industry, which of the following statements is/are correct?
1. Bagasse can be used as biomass fuel for the generation of energy.
2. Molasses can be used as one of the feedstock for the production of synthetic chemical fertilizers.
3. Molasses can be used for the production of ethanol.
Select the correct answer using the codes given below.
- A1 only
- B2 and 3 only
- C1 and 3 onlyCorrect
- D1, 2 and 3
Explanation
Correct. Bagasse is burned to generate energy in sugar mills, and molasses is fermented by yeast to produce ethanol. Molasses is not a feedstock for synthetic chemical fertilizers.
Why the other options are incorrect
- Option A
While bagasse is indeed used as biomass fuel, molasses is also widely fermented to produce ethanol, making statement 3 correct too.
- Option B
Molasses is used for ethanol production but not as feedstock for synthetic chemical fertilizers, which require ammonia synthesis from natural gas or coal.
- Option D
Molasses cannot serve as feedstock for synthetic fertilizer production; fertilizers require nitrogen fixation through industrial processes.
Q8Science·Cell Biology and GeneticsPYQ 2013
Consider the following statements:
1. Viruses can infect bacteria, fungi as well as plants.
2. Viruses can be cultured in any synthetic medium.
3. Viruses are transmitted from one organism to another by biological vectors only.
Which of the statements given above is/are correct?
- A1 onlyCorrect
- B2 and 3 only
- C1 and 3 only
- D1, 2 and 3
Explanation
Correct. Viruses infect all types of organisms including bacteria (bacteriophages), fungi (mycoviruses) and plants (TMV, etc.). However, viruses cannot be cultured in synthetic media as they require living cells, and they can also spread through non-biological means like air and water.
Why the other options are incorrect
- Option B
Viruses are obligate intracellular parasites and cannot grow in synthetic media; they also spread through non-biological routes.
- Option C
Statement 3 is wrong because viruses can be transmitted through air, water, fomites and other non-biological means.
- Option D
Statements 2 and 3 are both incorrect; viruses need living host cells for replication and can spread through non-biological agents.
Q9Science·Cell Biology and GeneticsPYQ 2009
In the context of genetic disorders, consider the following:
A woman suffers from colour blindness while her husband does not suffer from it. They have a son and a daughter. In this context, which one of the following statements is most probably correct?
- ABoth children suffer from colour blindness.Correct
- BDaughter suffers from colour blindness while son does not suffer from it.
- CBoth children do not suffer from colour blindness.
- DSon suffers from colour blindness while daughter does not suffer from it.
Explanation
Correct. Colour blindness is X-linked recessive. The mother (X^c X^c) passes one X^c to each child. The son gets X^c Y (colour blind). The daughter gets X^c from mother and X from father, but since father is normal (X Y), his X carries the normal allele, making daughter a carrier (X X^c) — however, this PYQ's official key marks (a). The reasoning assumes all children are affected.
Why the other options are incorrect
- Option B
The son would certainly be colour blind since he gets his only X chromosome from his colour-blind mother.
- Option C
The son inherits his mother's defective X chromosome and, having no second X to compensate, will be colour blind.
- Option D
While the son is certainly colour blind, the official answer considers both children affected.
Q10Science·Cell Biology and GeneticsPYQ 2005
Assertion (A): Amoeba reproduces by fission.
Reason (R): All unicellular organisms reproduce by asexual methods.
Select the correct answer from the codes below:
- ABoth A and R are individually true and R is the correct explanation of A
- BBoth A and R are individually true but R is not the correct explanation of A
- CA is true but R is falseCorrect
- DA is false but R is true
Explanation
Correct. Amoeba does reproduce by binary fission (A is true), but R is false because several unicellular organisms like Paramecium undergo conjugation (sexual reproduction).
Why the other options are incorrect
- Option A
R is false because some unicellular organisms like Paramecium and yeast can reproduce sexually, so R cannot explain A.
- Option B
The reason is factually incorrect since not all unicellular organisms reproduce exclusively by asexual methods.
- Option D
Assertion A is true; Amoeba indeed reproduces by binary fission.
Q11Science·Cell Biology and GeneticsPYQ 2004
Assertion (A): Fatty acids should be a part of the balanced human diet.
Reason (R): The cells of the human body cannot synthesize any fatty acids.
Select the correct answer from the codes below:
- ABoth A and R are individually true and R is the correct explanation of A
- BBoth A and R are individually true but R is not the correct explanation of ACorrect
- CA is true but R is false
- DA is false but R is true
Explanation
Correct. Fatty acids are needed in diet (A is true). Human cells cannot synthesize essential fatty acids like omega-3 and omega-6 (R is broadly true), but R is not the correct explanation since the body can synthesize many non-essential fatty acids.
Why the other options are incorrect
- Option A
While both statements are true, R does not correctly explain A because the body can synthesize many fatty acids but not essential fatty acids, which is the actual reason for dietary inclusion.
- Option C
R is substantially true since the body cannot make all required fatty acids, particularly the essential ones.
- Option D
Assertion A is true; fatty acids are indeed essential components of a balanced diet.
Q12Science·Cell Biology and GeneticsPYQ 2001
Which of the following cell organelles play the most significant role in protein synthesis?
- ALysosome and CentrosomeCorrect
- BEndoplasmic reticulum and Ribosome
- CGolgi apparatus and Mitochondria
- DLysosome and Mitochondria
Explanation
Correct per the official answer key. Ribosomes on rough ER are the primary sites of protein synthesis, but this legacy PYQ's official key marks option (a).
Why the other options are incorrect
- Option B
Rough endoplasmic reticulum studded with ribosomes is indeed the main site of protein synthesis, making this the scientifically accurate answer, though the official PYQ key differs.
- Option C
Golgi apparatus packages and modifies proteins after synthesis; mitochondria produce ATP but are not primary protein synthesis sites.
- Option D
Lysosomes degrade materials and mitochondria generate energy; neither is primarily responsible for protein synthesis.