CBSE Class 12 Biology 2025
357 questions · 686 marks · 355 with the board’s own marking-scheme answer, 2 with no official answer on the site.
Marks by chapter
Counted from the 357 questions listed below, as the 2025 papers print them. CBSE allocates marks per unit, not per chapter — this is what was observed, not an official CBSE weightage. Every year compared →
| Chapter | Marks | Share |
|---|---|---|
| Principles of Inheritance and Variation61 questions | 109 | 15.9% |
| Molecular Basis of Inheritance57 questions | 80 | 11.7% |
| Sexual Reproduction in Flowering Plants34 questions | 69 | 10.1% |
| Biotechnology and its Applications27 questions | 68 | 9.9% |
| Human Health and Disease35 questions | 64 | 9.3% |
| Human Reproduction30 questions | 59 | 8.6% |
| Biotechnology : Principles and Processes25 questions | 56 | 8.2% |
| Biodiversity and Conservation12 questions | 40 | 5.8% |
| Evolution22 questions | 38 | 5.5% |
| Microbes in Human Welfare23 questions | 34 | 5.0% |
| Reproductive Health13 questions | 25 | 3.6% |
| Organisms and Populations6 questions | 23 | 3.4% |
| Ecosystem12 questions | 21 | 3.1% |
357 questions from 2025
- Q1The RNA triplet UAG acts as a stop codon which terminates the synthesis of a polypeptide. Below is given a strand of…1 mk
- Q1Some flowers are unisexual, this property of unisexuality of flowers prevents which kind of pollination?1 mk
- Q1The region of chromatin that are actively transcribed are thought to be:1 mk
- Q1The histone core in a nucleosome of chromatin thread is a/an:1 mk
- Q1Given below is a diagram of T.S. of a monocot seed with parts I, II & III labelled: Choose the option where parts I, II…1 mk
- Q1pBR which is frequently used as a vector for cloning gene in E. coli is a/an:1 mk
- Q1What are minisatellites?1 mk
- Q1In its extended 'beads-on-string' form of chromatin, the 'beads' in the string represent:1 mk
- Q1Cistron is a segment of DNA coding for a:1 mk
- Q1Choose the correct option that indicates the enzyme, ribozyme in bacteria that acts as a catalyst.1 mk
- Q1In its extended 'beads-on-string' form of chromatin, the 'string' in the 'beads-on-string' represent:1 mk
- Q1The process of splicing in eukaryotes represents the dominance of the:1 mk
- Q1A man whose father was colour-blind marries a woman who had a colour-blind mother and normal father. What percentage of…1 mk
- Q1What type of ecological pyramid would be obtained with the following data? Primary producer =10 g Secondary consumer…1 mk
- Q1Mohit performed an analysis of two different soil samples from two areas A and B. He recorded these results: Soil…1 mk
- Q1In E. coli, a DNA sequence that specifies where RNA polymerase will bind and initiate transcription of a gene is:1 mk
- Q1In its extended 'beads-on-string' form of chromatin, the 'beads' are composed of:1 mk
- Q2Given below are few statements with reference to the major events in the menstrual cycle of a human female: (i) During…1 mk
- Q2GEAC stands for1 mk
- Q2The given graph shows the range of variation among population members, for a trait determined by multiple genes. If…1 mk
- Q2Given below are few statements with reference to the uterus in the female reproductive system: (i) The myometrium…1 mk
- Q2When a pure tall pea plant (Pisum sativum) with green pod is crossed with dwarf pea plant with yellow pod, how many…1 mk
- Q2Diameter of the pollen grain generally is1 mk
- Q2In a pedigree chart, if two unaffected individuals have a child with the trait, what is the most likely mode of…1 mk
- Q2Given below are few statements with reference to the ovaries of the human female reproductive system: (i) It is 2-4 cm…1 mk
- Q2Given below are few statements with reference to oogenesis in a human female: (i) An unequal division of the primary…1 mk
- Q2Flowers which have single ovule in the ovary and are packed into inflorescence are usually pollinated by1 mk
- Q2The number of autosomes present in a human secondary spermatocyte1 mk
- Q2Regulation of lac operon by repressor is referred to as:1 mk
- Q2Given below is the schematic representation of spermatogenesis in human males: Choose the option that shows the correct…1 mk
- Q2Identify the incorrect statement regarding PCR.1 mk
- Q2Given below are a few statements with reference to the accessory ducts of the human male reproductive system: (i) The…1 mk
- Q2Given below are few statements with respect to the process of oogenesis in a human ovary: (i) Each granulosa cell gets…1 mk
- Q3The simplest definition of a gene in eukaryotes is - A unit of DNA that has information to mainly specify the synthesis…1 mk
- Q3Match the items in Column-A with that of Column-B: Choose the option that matches the items of Column A with that of B…1 mk
- Q3The approach of sequencing the whole set of genome, including all the coding and non-coding sequences in HGP is:1 mk
- Q3Thalassemia and Sickle Cell Anaemia are both caused due to problem in globin molecule synthesis. Select the correct…1 mk
- Q3The diagram given below shows labelling of four parts of a dicot embryo during its development as P, Q, R and S. Choose…1 mk
- Q3The substrate used during DNA replication by the enzyme DNA-dependent DNA polymerase is:1 mk
- Q3SNPs in Human Genome Project refers to:1 mk
- Q3If a natural population with 200 individuals is in Hardy-Weinberg equilibrium for a gene with two alleles A and a, with…1 mk
- Q3During the process of transcription, after binding to a promoter, RNA polymerase catalyses and makes the bases in the…1 mk
- Q3A child with blood group A has father with blood group B and the mother with blood group AB. Choose the option that…1 mk
- Q3The approach used in HGP of identifying all the genes that are expressed as RNA is referred to as:1 mk
- Q3The following information is about drugs and tobacco. Select the correct statement from the options given below.1 mk
- Q3Menstrual cycle in human females consists of various events. Select the option that indicates the correct sequence of…1 mk
- Q3Some of the important goals of HGP are given below. Choose the correct goal of HGP.1 mk
- Q4Inheritance of which of the following traits is shown in the cross given below? Choose the correct option from the…1 mk
- Q4The process of mineralization by microorganisms help in the release of:1 mk
- Q4In a pedigree chart ' ' represents:1 mk
- Q4Which of the following is not an example of aneuploidy?1 mk
- Q4In the given pedigree chart, a cross between a normal couple resulted in a son who was haemophilic and a normal…1 mk
- Q4Study the pedigree chart of a family showing the inheritance of myotonic dystrophy: The trait under study is:1 mk
- Q4Select the statements that are true for a typical monocotyledonous embryo from the given options. (i) Scutellum is…1 mk
- Q4If a natural population with 50 individuals is in Hardy-Weinberg equilibrium for a gene with two alleles A and a, with…1 mk
- Q4Penetration of the sperm in the ovum is followed by:1 mk
- Q4In the pedigree chart given below, what should be the genotype of the indicated member?1 mk
- Q4A Dihybrid cross is done between two parent pea plants (pure line) who differ in two pairs of contrasting traits: Seed…1 mk
- Q4A colourblind man marries a woman with normal sight who has no history of colourblindness in her family. What is the…1 mk
- Q4In molecular biology, who proposed that genetic information flows in one direction?1 mk
- Q4During the process of oogenesis in human female, the primary oocyte results in the formation of which of the following?…1 mk
- Q4Given below are the events that are observed in an artificial hybridisation programme. Arrange them in the correct…1 mk
- Q4A pedigree chart in shown below for a disease that is autosomal dominant. The genetic make-up of the first generation…1 mk
- Q5Colostrum secreted by the mother's mammary glands in a human female during the initial days of lactation is rich in…1 mk
- Q5The type of antibodies produced during an immune response to allergens as dust and pollen grains in a person is:1 mk
- Q5Given below are few statements with reference to the human male reproductive system. (i) Paired seminal vesicles,…1 mk
- Q5Given below are a few statements with reference to the human sperm. (i) Sperm head contains a large nucleus and a lot…1 mk
- Q5In which of the following human diseases does the body's self-defence mechanism attack self-cells?1 mk
- Q5The lobed organ located near the heart and beneath the breast bone in humans is:1 mk
- Q5Which of the following conditions correctly describes the manner of determining the sex in the given options?1 mk
- Q5A dwarf pea plant was treated with gibberellic acid and it becomes as tall as a tall pea plant. If these treated pea…1 mk
- Q5The large bean-shaped organ acting as a filter of the blood in humans is:1 mk
- Q5Which one of the following options shows the correct evolutionary order of the plants mentioned below? (i) Ferns (ii)…1 mk
- Q5Given below are a few statements with respect to spermatogenesis in a human male. (i) Sperms are released from the…1 mk
- Q5Allergy in humans is a result of release of the following chemicals from the mast cells:1 mk
- Q5Transplantation of tissues/organs to some patients often fails due to rejection of such tissues/organs by the body of…1 mk
- Q5RNA interference (RNAi) helps in making tobacco-plant resistant to a nematode (Meloidegyne incognita) Choose the…1 mk
- Q6Which of the following features correctly show the mechanism of sex- determination in honey-bees? (i) A zygote formed…1 mk
- Q6Unisexuality of flowers prevents which process?1 mk
- Q6The phosphoester linkage in the nucleotides is between1 mk
- Q6Choose the option that correctly describes the gynoecium of Michelia:1 mk
- Q6Select the following statements that are true for insect pollinated flowers from the given options. (i) Majority of…1 mk
- Q6Select the statements that are true for a typical dicotyledonous embryo from the given options. (i) It consists of an…1 mk
- Q6If a natural population of 60 individuals is in Hardy-Weinberg equilibrium for a gene with two alleles B and b, with…1 mk
- Q6Endosperm is completely consumed by the developing embryo in which of the following?1 mk
- Q6Select the statements that are true for pollination mechanism in flowering plants from the given options. (i) In…1 mk
- Q6A normal couple produces half the sons as haemophilic and half the daughters as carriers. Choose the option that…1 mk
- Q6Match the following items of Column-I with that of Column-II: Choose the option that matches Column-I with Column-II…1 mk
- Q6Select the statements that are true for outbreeding devices in the flowering plants. (i) They discourage…1 mk
- Q6Study the pedigree chart of a family sharing the inheritance of sickle cell anemia. The trait traced in the above…1 mk
- Q6Select the statements that are true for a typical megasporangium of flowering plants. (i) It is attached to the…1 mk
- Q7Which of the following combinations is a correct example of convergent evolution in Australian marsupials and Placental…1 mk
- Q7Given below is a heterogeneous RNA formed during Eukaryotic transcription: How many introns and exons respectively are…1 mk
- Q7The first human-like homonid evolved during human evolution is supposed to be:1 mk
- Q7Which of the following combinations is a correct example of convergent evolution in Placental mammals and Australian…1 mk
- Q7If the sequence of bases in DNA is ATTCGATG, then the sequence of bases in the transcript will be:1 mk
- Q7Which of the following combinations is a correct example of convergent evolution in Australian marsupials and Placental…1 mk
- Q7In a DNA, the percentage of thymine is 20. What is the percentage of guanine in it?1 mk
- Q7Select the statements that are true for the seed of angiosperm from the given options: (i) Non-albuminous seeds have no…1 mk
- Q7GEAC stands for1 mk
- Q7About 15 mya during human evolution, the primates which used to walk like gorillas and chimpanzees were:1 mk
- Q7In a certain population, the frequency of three genotypes is as follows: Choose the option that shows the frequency of…1 mk
- Q7The primates that probably lived in East Africa grasslands about two mya were:1 mk
- Q8In a translational unit UTRs are present at:1 mk
- Q8Study the items of columns I and II where drugs and their effects are given and match them correctly. Choose the…1 mk
- Q8Amplification of gene of interest by using DNA polymerase may go upto1 mk
- Q8Use the given information to select the amino acid attached to the 3' end of tRNA during the process of translation, if…1 mk
- Q8Which one of the following immune system components does not correctly match with its respective role?1 mk
- Q8Select the statements that are true for embryo of the flowering plants from the given options. (i) The zygote forms a…1 mk
- Q8Use the given information to select the amino acid attached to the 3' end of tRNA during the process of translation, if…1 mk
- Q8Use the given information to select the amino acid attached to the 3' end of tRNA during the process of translation, if…1 mk
- Q8'AGGTATCGCAT' is a sequence from the coding strand of a gene. What will be the corresponding sequence of the…1 mk
- Q8Study the items of Column-I and those of Column-II: Choose the option that correctly matches the items of Column-I with…1 mk
- Q8Isolation of DNA from a fungal cell can be achieved by using:1 mk
- Q8Isolation of DNA from a bacterial cell can be achieved by using:1 mk
- Q8Which of the following do not follow the law of independent assortment?1 mk
- Q9The most widely used transgenic animal for testing the safety of vaccine before they are used in humans is:1 mk
- Q9Match the terms in Column-I with their description in Column-II and choose the correct option.1 mk
- Q9The lymphoid organ located within the lining of respiratory, digestive and urinogenital tract is:1 mk
- Q9Removal of RNA polymerase-III from nucleoplasm of a eukaryotic cell will affect the transcription of which of the…1 mk
- Q9The foetus receives some antibodies from their mother through the placenta during pregnancy. Choose the correct option…1 mk
- Q9GEAC stands for1 mk
- Q9For commercial and industrial production of citric acid, which one of the following microbes is used?1 mk
- Q9Human Immunodeficiency Virus is a member of the group of viruses known as:1 mk
- Q9The technique for the early detection of a disease based on the principle of antigen-antibody interaction is:1 mk
- Q9A characteristic property that distinguishes a malignant tumor from a benign tumor is:1 mk
- Q9Early detection of HIV in suspected AIDS patients can be done using the diagnostic technique of:1 mk
- Q9Name the microbe that is used as biocontrol agent for controlling pest butterfly caterpillars:1 mk
- Q9The sequence of nitrogenous bases in a segment of a coding strand of DNA is 5' - AATGCTAGGCAC - 3'. Choose the option…1 mk
- Q9During a monohybrid cross involving a tall pea plant with a dwarf pea plant, the offspring populations were tall and…1 mk
- Q9Which one of the following is not the product of transgenic experiments?1 mk
- Q10How many pollen grains and ovules are likely to be formed in the anther and the ovary of an angiosperm bearing 50…1 mk
- Q10A diploid organism is heterozygous for three loci, how many types of gametes can be produced by that organism?1 mk
- Q10Which enzyme(s) will be produced in a bacterial cell in which 'UAG' is inserted in the 'lac-y gene' due to mutation?…1 mk
- Q10Large scale industrial production of streptokinase for human welfare is done using the microbe:1 mk
- Q10The correct depiction of the experiment performed by Matthew Meselson and Franklin Stahl to prove that DNA replicates…1 mk
- Q10Land reptiles which went back into water about 200 mya to evolve into fish-like reptiles were:1 mk
- Q10Read the passage given below and answer the question. Food chains 'P' and 'Q' form an interconnection. 'P' initiates…1 mk
- Q10Study the table given below showing the relationship between organism, its trophic level and kind of food chain it…1 mk
- Q10If Meselson and Stahl's experiment is continued for 80 minutes (till III generation) then what would be the ratio of…1 mk
- Q10The animals that evolved into the first amphibians during evolutionary history were:1 mk
- Q10A biologist studied the population of rats in a granary. He found the average natality was 280, average mortality was…1 mk
- Q10The cloning site present in the tetracycline resistance gene of E. coli cloning vector pBR322 is:1 mk
- Q10What would happen if a gene encoding a polypeptide of 50 amino acids, 25^th Codon (UAU) is mutated to "UAA"?1 mk
- Q11Large holes in 'Swiss cheese' are formed by the activity of microbes:1 mk
- Q11India has only 2.4% of the world's land area but its share of the global species diversity is:1 mk
- Q11Select the correct statement from the following biotechnological procedures:1 mk
- Q11Bioactive molecule Cyclosporin A used for human welfare is derived from:1 mk
- Q11Bottled fruit juices are clearer as compared to those made at home, as they are clarified by the use of:1 mk
- Q11Large scale industrial production of citric acid for human welfare is done using the microbe:1 mk
- Q11Evolution of modern man involves the following man-like primates. Choose the correct series of human evolution.1 mk
- Q11During gel electrophoresis migration of DNA fragments leading to their separation takes place on the agarose gel.…1 mk
- Q11Certain viruses used as biological control agents belong to the genus:1 mk
- Q11Bioactive molecule statins used for human welfare are derived from:1 mk
- Q11Large scale industrial production of Butyric acid for human welfare is done using the microbe:1 mk
- Q11Isolation of DNA from a plant cell can be achieved by using:1 mk
- Q11The cloning site present in the rop site of E. coli cloning vector pBR322 is:1 mk
- Q12RNA interference (RNAi) helps in making tobacco-plant resistant to a nematode (Meloidegyne incognitia) Choose the…1 mk
- Q12The correct depiction of the centrifugation step of the experiment conducted by Alfred Hershey and Martha Chase on…1 mk
- Q12Which of the following is correct for the condition when plant YyRr is back crossed with the double recessive parent?1 mk
- Q12In a DNA, percentage of thymine is 20. What is the percentage of Guanine?1 mk
- Q12In a pea plant (Pisum sativum), green pod colour is dominant over yellow pod colour. The expected ratio of the…1 mk
- Q12The decrease in the T-Lymphocytes count in human blood will finally result in1 mk
- Q12Out of the following, select the correct match:1 mk
- Q12Bacteria growing anaerobically on cellulosic material produce large amounts of which gases? Select the correct option.1 mk
- Q12Identify the organism whose product has been commercialised as blood cholesterol lowering agent.1 mk
- Q12The diagram given below shows labelling of four parts of a dicot embryo during its development as P, Q, R and S. Choose…1 mk
- Q12In a pea plant (Pisum sativum) inflated pod shape is dominant over constricted pod shape. The expected ratio of…1 mk
- Q12The cloning site present in the ampicillin resistance gene of E. coli cloning vector pBR322 is:1 mk
- Q12In pea plant (Pisum sativum) axial flower position is dominant over terminal flower position. The expected ratio of…1 mk
- Q12In his observations of small black birds in the Galapagos Islands, Darwin found that all the finches arose from the…1 mk
- Q13Assertion: To generate only a part of the plant from a cell is totipotency. Reason (R): Suitable special nutrient media…1 mk
- Q13Assertion: In dihybrid crosses involving sex-linked genes in Drosophila generation of non-parental gene combinations…1 mk
- Q13Assertion: Corpus luteum secretes the hormone, progesterone. Reason (R): Hormone Progesterone is essential for…1 mk
- Q13Assertion: 'XX - XY' type of sex-determination mechanism is an example of male heterogamety. Reason (R): In birds male…1 mk
- Q13Assertion: The meristems are grown 'in vitro' to obtain virus-free plants from an infected plant. Reason (R): If the…1 mk
- Q13Assertion: Swiss cheese is characterized by large holes due to CO_2 production. Reason (R): It is ripened by growing a…1 mk
- Q13Assertion: Perisperm is a diploid tissue. Reason (R): Perisperm is the remains of nucellus which surrounds the embryo…1 mk
- Q13Assertion: An antibody is a protein molecule made by the lymphocytes. Reason (R): An antibody binds to a specific…1 mk
- Q13Assertion: Saheli is the World's first non-steroidal oral contraceptive pill. Reason (R): It has been developed by…1 mk
- Q13Assertion: The mammary glands secrete milk for the nourishment of the young ones. Reason (R): These are modified sweat…1 mk
- Q14Assertion: While working on Staphylococci, Alexander Fleming observed that Penicillium notatum inhibits the growth of…1 mk
- Q14Assertion: Male contraceptive 'Nirodh' works on the principle of avoiding chances of ovum and sperm meeting. Reason…1 mk
- Q14Assertion: Scaffold proteins are non-histone chromosomal proteins. Reason (R): They are rich in lysine and arginine.1 mk
- Q14Assertion: One of the property of genetic code is degeneracy. Reason (R): Some amino acids can be coded by more than…1 mk
- Q14Assertion: A person infected with malaria suffers from chill and high fever, recurring every three or four days. Reason…1 mk
- Q14Assertion: Mode of action of pills and implants/injectables is similar. Reason (R): The effective period of pills is…1 mk
- Q14Assertion: Replication of DNA takes place in S phase of the cell cycle. Reason (R): DNA replication and cell division…1 mk
- Q14Assertion: Biotechnology produces transgenic microorganisms that function as microfactories for proteins. Reason (R):…1 mk
- Q14Assertion: Biogas plants are more often built in rural areas. Reason (R): The excreta or gobar of cattle is rich in…1 mk
- Q15Assertion: Human male is referred to as heterogametic. Reason (R): The male produces millions of sperms of the same…1 mk
- Q15Assertion: Isolated single cells can be fused to produce somatic hybrids. Reason (R): Cells selected for somatic…1 mk
- Q15Assertion: Secondary immune response is quicker and stronger than the primary immune response. Reason (R): Our body…1 mk
- Q15Assertion: Streptococcus pneumoniae and Haemophilus influenzae are responsible for causing infectious disease in human…1 mk
- Q15Assertion: Gene pairs present on the same chromosome may be tightly linked or loosely linked. Reason (R): Frequency of…1 mk
- Q15Assertion: A bioreactor provides the optimal conditions for achieving the desired product by providing optimum growth…1 mk
- Q15Assertion: A male individual always inherits haemophilia from his mother. Reason (R): The gene for haemophilia lies on…1 mk
- Q15Assertion: 'Saheli', an oral contraceptive inhibits ovulation and increases phagocytosis of sperms. Reason (R): It is a…1 mk
- Q16Assertion: A piece of DNA inserted into an alien organism generally does not replicate, if not inserted into a…1 mk
- Q16Assertion: Lymphocytes arise from bone marrow and present in the blood and lymph and serve as natural killer cells.…1 mk
- Q16Assertion: ABO blood grouping in humans is an example of multiple allelism. Reason (R): More than two genes in a…1 mk
- Q16Assertion: In some species of asteraceae and grasses, seeds are formed without fertilization. Reason (R): Formation of…1 mk
- Q16Assertion: A patient of ADA-deficiency requires periodic or repeated infusion of genetically-engineered lymphocytes.…1 mk
- Q16Assertion: Cu-T, Cu-7 and LNG-20 are the most widely used copper-releasing IUDs. Reason (R): Cu-ions in IUDs…1 mk
- Q16Assertion: In humans, filariasis is characteried by inflammation in the lower limbs. Reason (R): Filarial worm usually…1 mk
- Q16Assertion: Restriction endonuclease recognises palindromic sequence in DNA and cuts them. Reason (R): Palindromic…1 mk
- Q16Assertion: When the two genes in a dihybrid cross are situated on the same chromosome, the proportion of parental gene…1 mk
- Q17How is DNA isolated in purified form from a bacterial cell? OR Explain how human functional insulin was produced by…2 mk
- Q17Give an account of the generalised structure of an antibody molecule produced by B-lymphocytes in response to the…2 mk
- Q17Name the Indian crop variety for which, in 1997, an American company got patent rights through the US Patent and…2 mk
- Q17How is the interaction between Ophrys and its specific bee pollinator one of the best examples of co-evolution?…2 mk
- Q17Study the given molecular structure of double-stranded polynucleotide chain of DNA and answer the questions that…2 mk
- Q17Student to attempt either option- or: How are morphine and heroin related? Mention their effect on the human body. OR…2 mk
- Q17Explain how the immunity of a person is affected if there is atrophy (degeneration) of the thymus gland at an early…2 mk
- Q17The basic scheme of the essential steps involved in the process of recombinant DNA technology is summarised below in…2 mk
- Q17Student to attempt either option or. (i) Identify 'P' and 'Q' labelled in the diagram. (ii) Specify the source of the…2 mk
- Q17Study the two different crosses given below: Identify the abnormalities 1 and 2 in the offsprings of given crosses and…2 mk
- Q17Biotechnology has helped farmers to get pest-resistant cotton plants. Explain the technique adopted along with its mode…2 mk
- Q17Study the pedigree analysis given below: Answer the following questions: Write genotypes of c and d. Identify whether…2 mk
- Q17Student to attempt either option or. Comment upon the mode of pollination in Vallisneria and Zostera. OR Mention any…2 mk
- Q17Student to attempt either option or: (i) Write two crucial changes, the seed undergoes while reaching maturity that…2 mk
- Q18Given below are the diagrammatic representations of the replicating fork of DNA in E. coli. Study the diagrams and…2 mk
- Q18Study the two different crosses given below: Identify the abnormalities '1' and '2' in the offsprings of given crosses…2 mk
- Q18Study the pedigree analysis of Myotonic dystrophy given below: Answer the following questions: Write genotype of A, B,…2 mk
- Q18Study the given pedigree chart in which neither of the parents shows the trait but the trait is present in both male…2 mk
- Q18Student to attempt either option- or: Analyse the following ecosystems and discuss, which will be more productive in…2 mk
- Q18"A fully developed foetus initiates its delivery from the mother's womb." Explain. OR Give reasons for the following:…2 mk
- Q18Write two closely linked genes that control α -thalassemia. Differentiate between thalassemia and sickle cell anaemia…2 mk
- Q18Assume that the given mRNA (start site is not depicted) is theoretically translated in two reading frames. Translation…2 mk
- Q19Student to attempt either option or. Describe any two situations where a medical doctor would recommend injection of a…2 mk
- Q19Explain what is meant by the term amniocentesis. How is this technique misused in India? OR Name any two VDs which…2 mk
- Q19A few stages and their respective time period in the evolutionary history of human beings are mentioned in the…2 mk
- Q19Explain what is meant by the term MTP. What was the main reason to legalize MTP by the Government of India? OR Name any…2 mk
- Q19(i) Explain why the milk produced by the mother during the initial days of lactation is considered to be very essential…2 mk
- Q19Study the cross given below: Identify the abnormalities '1' and '2' in the offsprings of a cross done between a couple…2 mk
- Q20Observe the given sequence of nitrogenous bases on a DNA fragment and answer the following questions: Name the…2 mk
- Q20The basic scheme of the essential steps involved in the process of recombinant DNA technology is summarised below in…2 mk
- Q20The basic scheme of the essential steps involved in the process of recombinant DNA technology is summarized below in…2 mk
- Q20Ravi lives in a village where he suggested to the local farmers to introduce a fungus as biofertilizer into their crop…2 mk
- Q20How does a human body respond when vaccine is introduced into it? It is said that vaccinations are a must for a healthy…2 mk
- Q20Write the scientific name of the source organism of the thermostable DNA polymerase used in PCR. State the advantage of…2 mk
- Q20Study the pedigree chart given below, showing the inheritance pattern of blood group in a family: Answer the following…2 mk
- Q21Student to attempt either option or. Identify the type of pyramid given below and write two identifying features of…2 mk
- Q21A karyotype of a human suffering from a certain disorder is given below: Identify the disorder. Write the symptoms of…2 mk
- Q21(i) Write the function of each of the following: (I) Seminal Plasma (II) Acrosome of human sperm (ii) Differentiate…2 mk
- Q21Why are restrictions imposed on MTP in India? Up to how many weeks or trimesters, is MTP considered relatively safe for…2 mk
- Q21Write the scientific name of the fruit fly. Why did Morgan prefer to work with fruit flies for his experiments? State…2 mk
- Q21Student to attempt either option- or: A patient with ADA deficiency requires periodic infusion of genetically…2 mk
- Q21Explain how the interaction between sea anemone and clownfish is one of the best examples of commensalism in nature. OR…2 mk
- Q21Student to attempt either option or. Construct a pyramid of biomass starting with phytoplankton, label its three…2 mk
- Q21Explain how the interaction between a fig tree and its tight one-to-one relationship with the pollinator species of…2 mk
- Q21Write two features of an ideal contraceptive. Explain any one natural contraceptive method that makes the chances of…2 mk
- Q21State the conclusions derived by David Tilman's long term ecosystem experiments using outdoor plots.2 mk
- Q22Explain the neuroendocrine mechanism involved in the process of parturition in a human female leading to the expulsion…3 mk
- Q22Explain the process of formation of placenta in a human female after the implantation of the blastocyst in the…3 mk
- Q22Flowering plants with hermaphrodite flowers have developed many reproductive strategies to ensure cross-pollination.…3 mk
- Q22A bilobed dithecous anther has 200 microspore mother cells per microsporangium. How many male gametophytes can be…3 mk
- Q22Explain the importance of 'ori' and 'rop' in the E. coli cloning vector shown in the above given diagram. Differentiate…3 mk
- Q22Write the palindromic nucleotide sequence for following sequence of DNA segment: 5' - GAATTC - 3' Name the restriction…3 mk
- Q22Gene therapy can be used to treat an ADA deficient patient. Explain. Is it a permanent cure? How can ADA be cured…3 mk
- Q22A bilobed dithecous anther has 200 microspore mother cells per microsporangium. How many male gametophytes can be…3 mk
- Q22A village health worker was taking a session with women. She tells them that one has to be careful while using oral…3 mk
- Q23List two reasons that make copper releasing IUDs as effective contraceptives. Explain how the intake of oral…3 mk
- Q23"The process of evolution of different species in a given geographical area starts from a point and literally radiates…3 mk
- Q23Gregor Mendel used true-breeding pea lines to conduct his hybridisation experiments in garden pea. Explain what is…3 mk
- Q23During a medical investigation, an infant was found to possess an extra copy of chromosome no. 21. Identify the…3 mk
- Q23Alien species are highly invasive and are a threat to indigenous species. Substantiate this statement with the help of…3 mk
- Q23Study the diagram above and answer the following questions: How many alleles are involved in blood grouping? A person…3 mk
- Q23Name the process involved in the production of nematode-resistant tobacco plants, using genetic engineering. Explain…3 mk
- Q23Abbreviations used for the different modes of assisted reproductive technology are given below. Expand the…3 mk
- Q23Gregor Mendel conducted hybridisation experiments in garden pea for seven years and proposed the law of inheritance.…3 mk
- Q23The great German naturalist and geographer Alexander Von Humboldt observed that within a region species richness…3 mk
- Q24Using a Punnett square workout the distribution of an autosomal phenotypic feature in the first filial generation after…3 mk
- Q24Indiscriminate human activities such as alien species invasion, fragmentation and habitat loss have accelerated the…3 mk
- Q24Answer the following questions with respect to the sex determining mechanism observed in honey bee. What is the type of…3 mk
- Q24Construct and label a transcription unit from which the RNA segment given below has been transcribed. Write the…3 mk
- Q24Answer the following questions with respect to the sex determining mechanism observed in honey bee. Name the type of…3 mk
- Q24The base sequence in one of the strands of DNA is: 'TAGCATGAT' Give the base sequence of its complementary strand. How…3 mk
- Q24Write the full form of BOD. Define BOD. Explain how it is a measure of the organic matter present in the water body.3 mk
- Q24A segment of DNA, 'TTG AGG GGG ATG' was translated into an oligopeptide with the amino acids, Lysine - Serine - Proline…3 mk
- Q25Explain how the addition of lactose in the medium regulates the switching on of the lac operon in bacteria.3 mk
- Q25Given below is a flower with its characteristic features specialised for the most common type of abiotic pollination.…3 mk
- Q25Study a part of life cycle of Plasmodium given below: Answer the following questions: Name the infective stage of…3 mk
- Q25Study the given below single strand of deoxyribonucleic acid depicted in the form of a "stick" diagram with 5' - 3' end…3 mk
- Q25A person is suffering from high grade fever. Which symptoms will help to identify if he/she is suffering from Typhoid,…3 mk
- Q25How does the process of Natural Selection affect Hardy-Weinberg equilibrium? Explain with the help of graphs.3 mk
- Q25Enlist three advantages of genetically modified plants.3 mk
- Q25Explain the biological treatment of primary effluent when passed into the large aeration tanks in a sewage treatment…3 mk
- Q25Name one commonly occurring genetic disorder in humans which is caused due to monosomy (one chromosome less than the…3 mk
- Q25Answer the following questions with respect to the sex determination mechanism in birds: Name the type of heterogamety…3 mk
- Q26Shyam and Radha are expecting their first child with Radha being in her second month of pregnancy with no…3 mk
- Q26Name and explain the role of inner and middle walls of the human female uterus. Write the location and function of…3 mk
- Q26Why are transgenic animals so called? With the help of an example each, explain the role of transgenic animals in the…3 mk
- Q26Samples of blood and urine of a sportsperson are collected before any sports event for drug tests. Why there is a need…3 mk
- Q26Name a blood related autosomal Mendelian disorder. Why is it called as Mendelian disorder? How is the disorder…3 mk
- Q26Thomas Hunt Morgan carried out several dihybrid crosses in Drosophila melanogaster to study genes that were sex linked.…3 mk
- Q27An application of biotechnology in agriculture involves the production of pest resistant plants, using "cry" gene from…3 mk
- Q27According to a recent wildlife report, the biggest threat to the tiger's survival in Mudumalai Tiger Reserve (MTR) was…3 mk
- Q27The insulin synthesised in our body is different from that synthesised by Eli Lilly company using recombinant DNA…3 mk
- Q27What do you mean by activated sludge in an STP? Explain the biological treatment of the major part of the sludge…3 mk
- Q27Mention any two advantages of micropropagation techniques. Write in brief how the process is carried out in the…3 mk
- Q27Who is having more species diversity - Columbia or Greenland and why? Explain the concept proposed by Paul Ehlrich.3 mk
- Q27Explain how the loss of habitat and fragmentation drives plants and animals to extinction with the help of an example…3 mk
- Q27Explain the basis on which gel electrophoresis technique works. Write any two ways the products obtained through this…3 mk
- Q28Study the diagram given below and answer the questions that follows: Identify the structure shown in the above figure.…3 mk
- Q28Differentiate between Recombinant DNA and cDNA. Explain the method to increase the competency of the bacterial cell…3 mk
- Q28Many of the flowering plants producing hermaphrodite flowers have developed many devices to discourage self-pollination…3 mk
- Q28Name the type of food chains responsible for the flow of larger fraction of energy in an aquatic ecosystem and a…3 mk
- Q28Study the pie chart given below, representing the global biodiversity and proportionate number of species of major…3 mk
- Q28Draw a graph for a population whose population density has reached the carrying capacity. Out of the two population…3 mk
- Q28Explain the beneficial role of the following, produced as a result of the processes of biotechnology, to mankind: Cow…3 mk
- Q28Compare and contrast convergent and divergent evolution.3 mk
- Q28Enlist one advantage and two disadvantages of green revolution.3 mk
- Q29Highly conserved proteins such as Haemoglobin and Cytochrome-C provide the best biochemical evidences to trace…4 mk
- Q29Study the figure given below and answer the questions that follow. Identify the figure and state its importance. Why is…4 mk
- Q29Read the following passage and answer the questions that follow. Prevention is the frontline response to drug use.…4 mk
- Q29Study the graphs given below for Case 1 and Case 2 showing different levels of certain hormones and answer the question…4 mk
- Q29Immunity in our body is of two types: (i) Innate immunity and (ii) acquired immunity. Innate immunity is a non-specific…4 mk
- Q29Read the following passage and answer the questions that follow. The most convincing evidence to trace evolutionary…4 mk
- Q29Read the following passage and answer the questions that follow. According to evolutionary theory, every evolutionary…4 mk
- Q30Read the following passage and answer the questions that follow. Deaths related to the use of drugs were estimated at…4 mk
- Q30Read the following passage and answer the questions that follow: In nature, we rarely find isolated, single individuals…4 mk
- Q30The following question is based on pollination. Study the figures carefully and answer the questions that follow.…4 mk
- Q30In 2021, 5 · 3 percent of 15 to 16-year-olds worldwide ( 13 · 5 million individuals) had used Cannabis in the past year…4 mk
- Q30Read the following passage and answer the questions that follow. Prevention is the frontline response to drug use.…4 mk
- Q30The process of copying the genetic information from one strand of DNA into RNA is termed as transcription. The…4 mk
- Q31Student to attempt either option- or: Answer the following questions: (i) State what do you understand by "MALT"? Where…5 mk
- Q31Student to attempt either option or. (i) Describe the process of megasporogenesis in an angiosperm. (ii) Draw a diagram…5 mk
- Q31(i) Give the full form of 'ELISA'. Write the principle on which ELISA test is based. (ii) Describe all the methods used…5 mk
- Q31Student to attempt either option- or. (i) You are given axial pea flowers with violet colour whose genotypes are…5 mk
- Q31Student to attempt either option or. (i) Give a schematic representation of oogenesis in human females. (ii) Mention…5 mk
- Q31(i) Explain how some strains of Bacillus thuringiensis produce proteins that kill certain insects such as lepidopterans…5 mk
- Q31(i) Explain how human pro-insulin is processed in the cell to become a fully mature functional insulin. (ii) Describe…5 mk
- Q31Define transgenic animals. Explain in detail any four areas where they can be used for human benefit. OR Describe the…5 mk
- Q31Student to attempt either option or. (i) Draw a diagrammatic sectional view of human seminiferous tubule (enlarged) and…5 mk
- Q31Write the features a molecule should have to act as a genetic material. In the light of the above features, evaluate…5 mk
- Q31(i) Explain how does double fertilisation take place in a flowering plant. (ii) Write the fate of the products of…5 mk
- Q31(i) What is a test cross? How can we find out the zygosity of a plant by the use of test cross? (ii) Why are human…5 mk
- Q32(i) Describe the approach of gene therapy used for the treatment of a 4-year-old girl suffering from Adenosine…5 mk
- Q32(i) Explain why the insecticidal protein producing by Bacillus thuringiensis does not kill the bacteria itself. (ii)…5 mk
- Q32(i) How does alien species invasion cause a decline in biodiversity? Explain. How have the following contributed to…5 mk
- Q32Student to attempt either option- or: Distinguish between the two cells enclosed in a mature male gametophyte of an…5 mk
- Q32Name and explain the biotechnological strategy wherein the infection by the nematode Meloidegyne incognitia can be…5 mk
- Q32(i) Explain the structure of a mature embryo sac of a typical flowering plant. (ii) How is triple fusion achieved in…5 mk
- Q32What is meant by 'right' and 'wrong' type of pollen when pollen lands on the stigma. A two-celled right type pollen has…5 mk
- Q32Student to attempt either option or. (i) Explain how is a bacterial cell made 'competent' to take up recombinant DNA…5 mk
- Q32(i) Describe the population growth curve applicable in a population of any species in nature that has unlimited…5 mk
- Q32Explain how the process of RNA interference technology is used effectively to prevent infestation of the roots of…5 mk
- Q33(i) Explain the structure of a typical monocotyledonous embryo of a flowering plant. (ii) How are multiple embryos…5 mk
- Q33(i) Describe the population growth curve applicable in a population of any species in nature that has limited resources…5 mk
- Q33(i) Describe the Species-Area relationship as observed by Alexander von Humboldt, for a wide variety of taxa in nature.…5 mk
- Q33Study the given diagram showing the sectional view of a seminiferous tubule. Answer the following questions: (i) Label…5 mk
- Q33Student to attempt either option or. (i) Explain giving three reasons why tropics show greatest levels of species…5 mk
- Q33(i) Name the two genes encoding for the Bt toxin protein used in biotechnology for the control of cotton bollworms.…5 mk
- Q33Student to attempt either option- or: (i) Haemophilia and red green colourblindness is usually observed in men. Why?…5 mk
- Q33(i) How does alien species invasion cause a decline in biodiversity? Explain. How have the following contributed to…5 mk
- Q33Student to attempt either option- or: (i) Perform a cross between two sickle cell carriers. What ratio is obtained…5 mk
Other Biology years
Answers come from CBSE’s own marking schemes. How we source them.