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ISC Class XII Board Examination

ISC Biology (Paper 1 — Theory) — Specimen Question Paper 2026

Official CISCE specimen question paper, published with its answer key, ahead of the ISC Class XII Board Examination 2026.

Specimen2026Subject code 863A
Open source paper at cisce.org (opens in a new tab)
Board
ISC Class XII Board Examination
Class
Class 12
Subject
Biology
Year
2026
Total marks
70 marks
Duration
Not verified

Verification and rights

Published by CISCE. Khojo Papers links to the original document rather than reproducing it.

ExamVault links to the paper published on cisce.org. The answer key is part of the same document. The document is CISCE copyright and is not reproduced here.

Official answer key

Questions in this paper

Section A

  1. 1((i))Answer the following questions briefly.
    Anita is suffering from dry and scaly lesions on various parts of the body. What is
    the biological name of the causative fungus?    1 mark
  2. 1((ii))Answer the following questions briefly.
    If the number of chromosomes in an endosperm is 12, then what will be the
    number of chromosomes in megaspore mother cell?    1 mark
  3. 1((iii))Answer the following questions briefly.
    Renu was conducting an experiment. She started with a single DNA strand and
    ran six cycles of PCR to produce number of molecules of DNA.    1 mark
  4. 1((iv))Answer the following questions briefly.
    At what stage of embryonic development, can the zygote be introduced in the
    Fallopian tube in ZIFT?    1 mark
  5. 1((v))Answer the following questions briefly.
    When a cross is made between tall plants with yellow seeds (TtYy) and tall
    plants with green seeds (Ttyy), what proportions of phenotype in the offspring
    could be expected to be tall plants with green seeds?    1 mark
  6. 1((vi))Answer the following questions briefly.
    A research scholar isolated a new restriction enzyme from Thermus aquaticus
    strain YT3. It was the fourth restriction enzyme discovered from this strain.
    Propose a scientifically accurate name for this enzyme using the standard
    nomenclature rules.    1 mark
  7. 1((vii))Answer the following questions briefly.
    Construct a pyramid of numbers for an ecosystem in which a single large aquatic
    plant supports a population of small herbivorous fish, which are consumed by a
    larger population of predatory fish such as kingfish.    1 mark
  8. 1((viii))Answer the following questions briefly.
    Observe the relation between the first two words and then complete the analogy.
    Chikungunya: Aedes :: Malaria: ________.    1 mark
  9. 1((ix))Answer the following questions briefly.
    A young boy named Arjun has sickle-shaped red blood cells. He experiences
    frequent fatigue, and shows signs of damage to kidney. Genetic analysis reveals
    a single point mutation in the gene coding for β-globin.
    Which one of the following genetic phenomena is MOST LIKELY responsible
    for the multiple symptoms observed in Arjun?    1 mark
  10. 1((x))Answer the following questions briefly.
    Kiwi is a dioecious species. Which of the following methods can be definitely
    ruled out as a possible mode of pollination in that case?
    (P) Cleistogamous autogamy
    (Q) Chasmogamous autogamy
    (R) Geitonogamy
    (S) Xenogamy    1 mark
  11. 1((xi))Answer the following questions briefly.
    Given below are two statements marked Assertion and Reason. Read both the
    statements carefully and choose the correct option.
    Assertion: An amino acid in polypeptide chain is not always altered even due
    to change in the third nitrogenous base of codon.
    Reason: The amino acid does not change due to degeneracy of genetic code.    1 mark
  12. 1((xii))Answer the following questions briefly.
    Given below are two statements marked Assertion and Reason. Read both the
    statements carefully and choose the correct option.
    Assertion: ‘Bt’ toxin gene has been cloned from bacteria E.coli and expressed
    in plants to provide resistance from insect without the need of
    insecticides.
    Reason: ‘Bt’ toxin is produced in a crystalline state by the above-mentioned
    bacterium.    1 mark
  13. 1((xiii))Answer the following questions briefly.
    Why are tendrils of vine (Vitis) and pea (Pisum) considered to be analogous
    organs?    1 mark
  14. 1((xiv))Answer the following questions briefly.
    Ravi wanted to grow rice in his field. He was very concerned about environment
    degradation, so he did not want to use chemical fertilisers. Suggest a suitable
    biological method to Ravi.    1 mark
  15. 1((xv))Answer the following questions briefly.
    Answer the following:
    (a) Expand the abbreviation NPP.
    (b) Rule of Equivalence states that in DNA, adenine equals thymine and
    guanine equals cytosine. This is due to base pairing in double helix. thus,
    purines equal pyrimidines. Which scientist offered this concept?    2 marks
  16. 1((xvi))Answer the following questions briefly.
    A bilobed dithecous anther has 100 microspore mother cells per
    microsporangium. How many male gametophytes can this anther produce?    1 mark
  17. 1((xvii))Answer the following questions briefly.
    The diagram given below represents a specific stage of gestation period. Identify
    the structure labelled - B.    1 mark
  18. 1((xviii))Answer the following questions briefly.
    Give a reason for each of the following statements:
    (a) Sameer drew a diagram of human sperm and showed it to his teacher.
    The teacher rejected the diagram.
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    ISC (CLASS XII) SPECIMEN QUESTION PAPER 2026
    (b) Even under similar environmental conditions, decomposition of the
    exoskeleton of millipedes occurs more slowly than the leaves.    2 marks

Section B

  1. 2((i))Construct an ideal pyramid of energy when 1000,000 joules of sunlight is
    available. Label all its trophic levels.
    OR
  2. 2((ii))The graph given below is based on the data collected from a survey conducted on
    species richness of a group of mammals in three different climatic regions of the
    world: Brazil, France and Norway. Brazil has nearly 540 species of mammals,
    France has nearly 303 species of mammals and Norway has 65 species of
    mammals.
    Species Richness
    O Polar (N) Temperate (N) Tropical
    region region region
    (a) Based on the species richness, identify the location of these countries in
    the respective climatic regions shown in the graph.
    (b) In which climatic region, will you place India?
  3. 3((i))2] Given below is the relationship between the HIV levels in the blood and helper T-cell count in a person detected with AIDS. Study the relationship and answer the questions that follow. --------------------------------------------------------------------------------------------------------------------- ISC (CLASS XII) SPECIMEN QUESTION PAPER 2026 Visit CollegeDekho
    Describe the trend observed between viral load and immune response following
    initial infection.
  4. 3((ii))2] Given below is the relationship between the HIV levels in the blood and helper T-cell count in a person detected with AIDS. Study the relationship and answer the questions that follow. --------------------------------------------------------------------------------------------------------------------- ISC (CLASS XII) SPECIMEN QUESTION PAPER 2026 Visit CollegeDekho
    Is the virus permanently eliminated from the body? Justify your answer.
  5. 5((i))2] Study the diagram given below and answer the following questions:
    Identify the anode end in the diagram.
  6. 5((ii))2] Study the diagram given below and answer the following questions:
    How are these DNA fragments visualised?
  7. 6((i))2] Microbes especially yeasts have been used from time immemorial for the production of beverages like wine, beer, whisky brandy, or rum. Depending on the type of the raw materials used for fermentation and type of processing (with or without distillation) different types of alcoholic drinks are obtained.
    Mention the scientific name of the organism used to prepare fermented beverages.
  8. 6((ii))2] Microbes especially yeasts have been used from time immemorial for the production of beverages like wine, beer, whisky brandy, or rum. Depending on the type of the raw materials used for fermentation and type of processing (with or without distillation) different types of alcoholic drinks are obtained.
    Name any one beverage obtained without distillation of fermented broth.
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    ISC (CLASS XII) SPECIMEN QUESTION PAPER 2026
  9. 7((i))Ryan had developed a GM organism. Which government organisation will he
    approach to obtain the clearance for its mass production?
  10. 7((ii))Which bioactive product is used for the treatment of emphysema?
  11. 8((i))In a barn, there were 30 rats. 5 more rats entered the barn and 6 of the rats were
    eaten by the cats in one week. If 8 rats were born during the same period, and
    during the same time, 7 rats left the barn, find the resultant rat population in the
    barn at the end of one week.

Section C

  1. 9((i))3] Study the pedigree chart given below showing the pattern of blood group inheritance in a family.
    State the genotypes of the following:
    (a) Parents
    (b) The individual ‘X’ in the second generation
  2. 9((ii))3] Study the pedigree chart given below showing the pattern of blood group inheritance in a family.
    State the possible blood group(s) of the individual ‘Y’ in 3rd generation.
  3. 10((i))Darwin’s finches are best example of adaptive radiation. Justify.
    OR
  4. 10((ii))(a) The recessive allele ‘b’ occurs with a frequency of 0·8 in a population of
    moths that is in Hardy Weinberg Equilibrium. What is the frequency of
    homozygous dominant individuals?
    (b) List any two differences between Homo habilis and Homo erectus.
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    ISC (CLASS XII) SPECIMEN QUESTION PAPER 2026
  5. 12((i))3] A twenty-year old boy, Reshu has become addicted to alcohol.
    Mention any two possible reasons for his alcohol addiction.
  6. 12((ii))3] A twenty-year old boy, Reshu has become addicted to alcohol.
    Suggest any one measure by which addiction can be prevented.
  7. 13((i))3] A scientist is attempting to create a recombinant DNA molecule by combining a plasmid vector and a foreign DNA. A plasmid DNA and a linear DNA of the same size have a single site for the restriction enzyme EcoRI. When cut by the same RE and separated by gel electrophoresis, the plasmid shows one DNA band, and the linear DNA shows two bands.
    What causes the difference between the number of DNA bands generated from
    the plasmid and from the linear DNA?
  8. 13((ii))3] A scientist is attempting to create a recombinant DNA molecule by combining a plasmid vector and a foreign DNA. A plasmid DNA and a linear DNA of the same size have a single site for the restriction enzyme EcoRI. When cut by the same RE and separated by gel electrophoresis, the plasmid shows one DNA band, and the linear DNA shows two bands.
    What is the advantage of using agarose in gel electrophoresis?
  9. 13((iii))3] A scientist is attempting to create a recombinant DNA molecule by combining a plasmid vector and a foreign DNA. A plasmid DNA and a linear DNA of the same size have a single site for the restriction enzyme EcoRI. When cut by the same RE and separated by gel electrophoresis, the plasmid shows one DNA band, and the linear DNA shows two bands.
    How does EcoRI differ from an exonuclease?
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    ISC (CLASS XII) SPECIMEN QUESTION PAPER 2026
  10. 14((i))3] Study the diagram given below that shows the modes of pollination and answer the questions that follow.
    The given diagram shows three methods of pollination in plants. What are the
    technical terms used for pollen transfer methods labelled ‘2’ and ‘3’?
  11. 14((ii))3] Study the diagram given below that shows the modes of pollination and answer the questions that follow.
    How does Salvia achieve pollination successfully?

Section D

  1. 16((i))5] During a field excursion, a group of class XII students visited Kaziranga National Park and observed efforts to protect the Indian rhinoceros in its natural habitat. They also toured a botanical garden and a gene bank, where they saw endangered plant species and preserved seeds. Based on this context, answer the following questions:
    Name and define the two types of conservation methods mentioned above.
  2. 16((iii))5] During a field excursion, a group of class XII students visited Kaziranga National Park and observed efforts to protect the Indian rhinoceros in its natural habitat. They also toured a botanical garden and a gene bank, where they saw endangered plant species and preserved seeds. Based on this context, answer the following questions:
    Is Captive breeding an ex-situ or an in-situ strategy. Justify your answer with a
    reason.
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    ISC (CLASS XII) SPECIMEN QUESTION PAPER 2026
  3. 17((i))(a) Write a brief note on Griffith’s experiment. What was the conclusion drawn
    from this experiment?
    (b) Name the parts ‘A’ and ‘B’ of the transcription unit shown below.
    OR
  4. 17((ii))Study the diagram given below and answer the questions that follow.
    (a) Name the molecule ‘X’ synthesised by ‘I’ gene. How does this molecule
    get inactivated?
    (b) Name the enzymes coded respectively by genes- z, y, and a.
    (c) Which enzyme binds to the operator to initiate transcription?
  5. 18((i))The following graph represents the relative concentrations of the four hormones
    present in the blood plasma of a woman during her menstrual cycle.
    Identify the hormones A, B, C and D.
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    ISC (CLASS XII) SPECIMEN QUESTION PAPER 2026
  6. 18((ii))During a fertility consultation, a woman mentions her menstrual cycle lasts for
    33 days regularly. To help her conceive, the doctor advised her to track ovulation.
    On which day of the menstrual cycle is she most likely to ovulate?
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    ISC (CLASS XII) SPECIMEN QUESTION PAPER 2026
    BIOLOGY
    PAPER 1
    (THEORY)