Haryana Board Class 12 Biology Annual Exam 2026 – Solved Paper
Download PDF HBSE Class 12th Biology Question Paper 2026
Section – A: Objective Type Questions
Q1. Pollen grains retain viability for months in plants belonging to which families?
Answer: (A) Solanaceae, Leguminosae and Liliaceae
Q2. The structure of a bilobed anther consists of:
Answer: (D) 2 thecae and 4 sporangia
A typical bilobed anther has two thecae, and each theca contains two pollen sacs or microsporangia. Therefore, there are four microsporangia in total.
Q3. Terminator codon is:
Answer: (D) All of these
The three stop codons are UAA, UAG and UGA.
Q4. Which one of the following will not allow a molecule to act as genetic material?
Answer: (D) Ability to easily break down structurally and chemically
Q5. Which one is the pathogen of amoebic dysentery?
Answer: (D) Entamoeba histolytica
Q6. Which bacterial species acts as a bio-insecticide?
Answer: (B) Bacillus thuringiensis
Q7. Which enzyme is used to dissolve the fungal cell wall?
Answer: (C) Chitinase
Fungal cell walls contain chitin. Chitinase breaks down chitin and therefore helps in dissolving the fungal cell wall.
Q8. Primary productivity in an ecosystem is expressed as:
Answer: (A) g m−2 yr−1
Q9. The starting point in a detritus food chain is:
Answer: (B) Dead organic matter
Q10. Name the oral pill which is taken by Indian women once a week.
Answer: Saheli
Saheli is a non-steroidal oral contraceptive pill that was developed in India.
Q11. Mention the type of evolution responsible for the similarity seen in potato tuber and sweet potato.
Answer: Convergent evolution
Potato tuber and sweet potato are structurally different organs but perform a similar storage function. Such similarity due to adaptation to similar functions is an example of convergent evolution.
Q12. What is the botanical name of baker's yeast?
Answer: Saccharomyces cerevisiae
Q13. Zygote divides to form __________ which is implanted in the uterus.
Answer: Blastocyst
Q14. __________ is a cross between an organism of unknown genotype and a homozygous recessive organism.
Answer: Test cross
Q15. Large-scale production of biotechnological products involves the use of __________.
Answer: Bioreactors
Q16. Assertion and Reason
Assertion (A): Medical termination of pregnancy (MTP) is done to get rid of unwanted pregnancies.
Reason (R): It is usually done after 24 weeks of pregnancy.
Answer: (C) Assertion is true, but Reason is false.
MTP may be used to terminate an unwanted pregnancy under appropriate medical and legal conditions. The statement that it is usually done after 24 weeks is incorrect.
Q17. Assertion and Reason
Assertion (A): For DNA sequencing, the total DNA from a cell is isolated and converted into random fragments of relatively smaller sizes.
Reason (R): The human genome contains approximately 3 × 109 base pairs and sequencing the entire genome is a large task.
Answer: (B) Both A and R are true, but R is not the correct explanation of A.
Q18. Assertion and Reason
Assertion (A): In bioreactors, raw materials are biologically converted into desired products.
Reason (R): Bioreactors provide optimum growth conditions for microorganisms such as temperature, pH, substrate and salts.
Answer: (A) Both A and R are true, and R is the correct explanation of A.
Section – B: Very Short Answer Type Questions
Q19. State the role of a biolistic gun in biotechnology experiments. Microparticles of which element are used?
Answer: A biolistic gun, or gene gun, is used to introduce foreign DNA directly into plant cells. DNA-coated microscopic particles are accelerated and delivered into the target cells.
The microparticles are generally made of gold or tungsten.
Q20. Differentiate between perisperm and pericarp.
| Perisperm | Pericarp |
|---|---|
| It is the persistent nucellus present in a seed. | It is the wall of the fruit developed from the ovary wall. |
| It is a seed structure. | It is a fruit structure. |
OR – Differentiate between hypocotyl and epicotyl.
| Hypocotyl | Epicotyl |
|---|---|
| It is the embryonic region below the cotyledons. | It is the embryonic region above the cotyledons. |
| It connects the radicle with the cotyledons. | It connects the plumule with the cotyledons. |
Q21. Why are both strands of DNA not copied during transcription?
Answer: If both DNA strands were transcribed, two complementary RNA molecules would be produced. They could pair with each other and form double-stranded RNA, which would interfere with translation. Therefore, only one DNA strand acts as the template for transcription of a particular gene.
Q22. Describe phenylketonuria.
Answer: Phenylketonuria is an inherited metabolic disorder caused by deficiency of the enzyme phenylalanine hydroxylase. As a result, phenylalanine cannot be properly converted into tyrosine and accumulates in the body. Its accumulation can affect brain development and cause intellectual disability if untreated. It is inherited as an autosomal recessive disorder.
OR – Brief account of mutation:
A mutation is a sudden, stable and heritable change in the genetic material of an organism. Mutations may occur naturally or may be induced by physical or chemical mutagens. They can involve changes in a gene or larger changes in chromosomes.
Q23. Name the primary and secondary lymphoid organs.
Primary lymphoid organs: Bone marrow and thymus.
Secondary lymphoid organs: Spleen, lymph nodes, tonsils, Peyer's patches and other lymphoid tissues.
Q24. Draw a well-labelled diagram of E. coli cloning vector pBR322 showing restriction sites and antibiotic-resistant genes.
Answer: pBR322 is a plasmid cloning vector containing two antibiotic-resistance genes:
- ampR – ampicillin resistance gene
- tetR – tetracycline resistance gene
Important restriction sites include EcoRI, BamHI, SalI, PstI, PvuI and PvuII. The vector also contains the ori (origin of replication).
OR – Why does Bt toxin not kill Bacillus but kill insects?
Bt bacteria produce the toxin as an inactive protoxin. In the alkaline environment of the insect gut, the protoxin is activated and damages the intestinal lining. The conditions inside the bacterium do not activate the toxin in the same way, so the bacterium is not killed by its own toxin.
Q25. Identify a and b in the given figure representing the proportionate number of major vertebrates.
Answer: Based on the figure, a = fishes and b = reptiles.
Section – C: Short Answer Type Questions
Q26. Define ecological pyramid and describe pyramid of number and biomass with examples.
Answer: An ecological pyramid is a graphical representation of the trophic structure of an ecosystem. It may represent the number of organisms, biomass or energy at different trophic levels.
Pyramid of number: It represents the number of organisms present at each trophic level. For example, in a grassland ecosystem, many grasses support fewer herbivores, which support still fewer carnivores. It is generally upright.
Pyramid of biomass: It represents the total dry weight or living matter present at each trophic level. It is generally upright in terrestrial ecosystems. In some aquatic ecosystems, the pyramid of biomass may be inverted because phytoplankton have a small standing biomass but reproduce rapidly.
Q27. Describe ex-situ conservation of biodiversity.
Answer: Ex-situ conservation means conserving organisms outside their natural habitats. It is useful when species are threatened in their natural environment.
- Endangered plants may be maintained in botanical gardens and seed banks.
- Animals may be protected in zoos and breeding centres.
- Germplasm can be preserved through seed banks, tissue culture and cryopreservation.
This method helps in the conservation and possible reintroduction of threatened species.
OR – Major causes of species loss in a geographical region:
- Habitat loss and fragmentation
- Over-exploitation of natural resources
- Invasion by alien species
- Co-extinctions
Q28. Name the bioactive molecules produced by Streptococcus, Monascus and Trichoderma.
- Streptococcus: Streptokinase
- Monascus: Statins
- Trichoderma: Cyclosporin A
Q29. Differentiate between divergent and convergent evolution.
| Divergent Evolution | Convergent Evolution |
|---|---|
| Related organisms develop different adaptations. | Unrelated organisms develop similar adaptations. |
| It produces homologous structures with different functions. | It produces analogous structures with similar functions. |
| Example: forelimbs of humans, whales and bats. | Example: wings of birds and butterflies. |
Q30. Describe the important goals of the Human Genome Project.
Answer: The major goals of the Human Genome Project were:
- To identify all the genes present in the human genome.
- To determine the complete sequence of approximately 3 billion base pairs of human DNA.
- To store the information obtained in databases.
- To improve tools for data analysis.
- To understand the ethical, legal and social issues related to genome information.
OR – Three applications of DNA fingerprinting:
- Identification of individuals in forensic investigations.
- Establishing biological relationships such as parentage.
- Identification of individuals or human remains.
Section – D: Case Based Questions
Q31. Case Study – Infertility
An infertile couple has a very low sperm count in the male. The female has a blocked oviduct and spermicidal secretions in the vagina but can provide a suitable environment for embryo development.
(i) What is infertility?
Answer: Infertility is the inability of a couple to conceive a child despite regular unprotected sexual intercourse for a reasonable period, commonly one year.
(ii) What treatment options are available for low sperm count?
Answer: Assisted reproductive techniques such as IUI and ICSI may be used depending on the severity and cause of infertility. In ICSI, a selected sperm is directly injected into the ovum.
OR – What are ICSI and IUI?
- ICSI: Intracytoplasmic sperm injection, in which a single sperm is injected directly into an ovum.
- IUI: Intrauterine insemination, in which prepared semen is introduced directly into the uterus.
(iii) Suggest the ART used in the above case.
Answer: In vitro fertilisation followed by embryo transfer (IVF-ET) is suitable because the female has a blocked oviduct but can support embryo development. Depending on the sperm condition, ICSI may be used for fertilisation.
Q32. Case Study – Drug Abuse
Rahul, a 17-year-old student, has started experimenting with cannabis. He experiences temporary euphoria and withdrawal symptoms when trying to stop. His habit affects his studies and relationships.
(i) What is a cannabinoid drug?
Answer: Cannabinoids are psychoactive substances obtained from the Cannabis sativa plant. They affect the central nervous system and can produce changes in mood, perception and behaviour.
(ii) How did drug abuse affect Rahul's life?
Answer: Drug abuse affected Rahul's studies and relationships. His dependence also caused withdrawal symptoms when he attempted to stop using the drug.
OR – What can help drug addicts recover?
Recovery may involve medical supervision, counselling, behavioural therapy, family support and rehabilitation programmes.
(iii) What are the psychological effects of drug abuse?
Answer: Drug abuse may cause mood changes, impaired judgement, anxiety, depression, behavioural changes, dependence and difficulty in maintaining normal social and academic activities.
Section – E: Long Answer Type Questions
Q33. (a) Give a schematic representation showing the events of spermatogenesis in humans.
Answer:
Spermatogonium (2n) → Primary spermatocyte (2n) → Meiosis I → Two secondary spermatocytes (n) → Meiosis II → Four spermatids (n) → Spermiogenesis → Spermatozoa (n)
During spermatogenesis, diploid spermatogonia develop into haploid spermatozoa through meiotic divisions and subsequent differentiation.
(b) Describe the structure of human sperm.
A mature human sperm is a microscopic, haploid male gamete. It has four main parts:
- Head: Contains the haploid nucleus and an acrosome. The acrosome contains enzymes that help the sperm penetrate the ovum.
- Neck: Connects the head with the middle piece.
- Middle piece: Contains numerous mitochondria that provide energy for movement.
- Tail: Helps in the movement of sperm.
OR – Describe the structure of pollen grain in detail.
A pollen grain represents the male gametophyte of flowering plants. It is generally surrounded by two wall layers:
- Exine: The outer layer is made mainly of sporopollenin. It is highly resistant and has characteristic sculpturing and germ pores.
- Intine: The inner wall is made mainly of cellulose and pectin.
A mature pollen grain commonly contains a large vegetative cell and a smaller generative cell. The generative cell later divides to form two male gametes. During pollination, the pollen grain reaches the stigma and may germinate to form a pollen tube.
Q34. What is an operon? Explain the lac-operon model in E. coli.
Answer: An operon is a functional unit of DNA containing a group of genes regulated together and transcribed as a single unit.
The lac operon of Escherichia coli controls the metabolism of lactose. It consists mainly of a regulatory gene, promoter, operator and structural genes.
- The structural genes are lacZ, lacY and lacA.
- In the absence of lactose, the repressor protein binds to the operator and prevents transcription of the structural genes.
- When lactose is available, its derivative allolactose acts as an inducer and binds to the repressor.
- The repressor becomes inactive and leaves the operator.
- RNA polymerase can then transcribe the structural genes, producing enzymes required for lactose utilisation.
Thus, the lac operon is an example of an inducible operon and provides efficient regulation of gene expression.
OR – Give a brief account of transcription in prokaryotes.
Transcription is the process of formation of RNA using one strand of DNA as a template. In prokaryotes, RNA polymerase carries out transcription.
- Initiation: RNA polymerase recognises and binds to the promoter region of DNA.
- Elongation: The DNA strands locally separate and RNA polymerase synthesises RNA in the 5′ to 3′ direction using the template strand.
- Termination: When a termination signal is reached, the newly formed RNA is released and transcription ends.
In prokaryotes, transcription and translation can occur simultaneously because there is no nuclear membrane separating the genetic material from the cytoplasm.
Q35. What is gene therapy? Illustrate using the example of ADA deficiency.
Answer: Gene therapy is a technique in which a functional gene is introduced into a patient's cells to correct or compensate for a defective gene.
ADA deficiency is caused by a defect in the gene coding for the enzyme adenosine deaminase (ADA). The deficiency can lead to severe immunodeficiency.
In one approach, functional ADA cDNA is introduced into the patient's lymphocytes using a suitable vector. The genetically corrected cells are then returned to the patient. These cells can produce functional ADA and help improve immune function.
Because lymphocytes have a limited life span, repeated treatment may be required. A more lasting approach is to introduce the functional gene into suitable bone-marrow-derived stem cells.
OR – Compare the advantages and disadvantages of genetically modified crops.
| Advantages | Disadvantages |
|---|---|
| Can provide resistance against insect pests. | May raise concerns about effects on non-target organisms. |
| Can reduce crop losses and improve productivity. | Long-term ecological effects require careful assessment. |
| Can provide resistance to certain diseases or environmental stresses. | Development and regulation of GM crops can be costly. |
| Can improve nutritional quality in selected crops. | Possible gene flow to related plants needs to be monitored. |
Therefore, genetically modified crops can offer important agricultural benefits, but their environmental, health and socio-economic aspects should be carefully evaluated.