CBSE Class 12 Biology 2025
355 questions · 684 marks · every one with the board’s own marking-scheme answer.
What 2025 actually asked, chapter by chapter
Marks we counted in the 2025 papers themselves. CBSE allocates marks per unit, not per chapter — this is what was observed, not an official CBSE weightage.
| 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 | 9.4% |
| Human Reproduction29 questions | 58 | 8.5% |
| Biotechnology : Principles and Processes25 questions | 56 | 8.2% |
| Biodiversity and Conservation12 questions | 40 | 5.8% |
| Evolution22 questions | 38 | 5.6% |
| Microbes in Human Welfare22 questions | 33 | 4.8% |
| Reproductive Health13 questions | 25 | 3.7% |
| Organisms and Populations6 questions | 23 | 3.4% |
| Ecosystem12 questions | 21 | 3.1% |
All 355 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 mkasked 2×
- Q1pBR which is frequently used as a vector for cloning gene in E. coli is a/an:1 mk
- Q1What are minisatellites?1 mkasked 2×
- 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 mkasked 3×
- 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
- Q2GEAC stands for1 mk
- Q2The given graph shows the range of variation among population members, for a trait determined by multiple genes. If…1 mkasked 2×
- 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 mkasked 2×
- 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 mkasked 2×
- 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 mkasked 2×
- 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 mkasked 3×
- 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 mkasked 3×
- 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 mkasked 2×
- 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 mkasked 2×
- 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 mkasked 3×
- 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 mkasked 3×
- 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 mkasked 3×
- 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 mkasked 3×
- 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 mkasked 3×
- 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 mkasked 2×
- 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 mkasked 3×
- 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 mkasked 2×
- 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 mkasked 3×
- 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 mkasked 2×
- 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 mkasked 3×
- 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 mkasked 3×
- 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 mkasked 3×
- Q11Select the correct statement from the following biotechnological procedures:1 mkasked 2×
- 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 mkasked 3×
- 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 mkasked 2×
- Q12Out of the following, select the correct match:1 mkasked 3×
- 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 mkasked 3×
- Q13Assertion: In dihybrid crosses involving sex-linked genes in Drosophila generation of non-parental gene combinations…1 mkasked 3×
- Q13Assertion: Corpus luteum secretes the hormone, progesterone. Reason (R): Hormone Progesterone is essential for…1 mkasked 2×
- 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 mkasked 3×
- Q13Assertion: Swiss cheese is characterized by large holes due to CO 2 production. Reason (R): It is ripened by growing a…1 mkasked 3×
- 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 mkasked 2×
- 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 mkasked 2×
- Q14Assertion: A person infected with malaria suffers from chill and high fever, recurring every three or four days. Reason…1 mkasked 3×
- 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 mkasked 2×
- 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 mkasked 2×
- 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 mkasked 3×
- 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 mkasked 2×
- Q15Assertion: Gene pairs present on the same chromosome may be tightly linked or loosely linked. Reason (R): Frequency of…1 mkasked 3×
- Q15Assertion: A bioreactor provides the optimal conditions for achieving the desired product by providing optimum growth…1 mkasked 3×
- Q15Assertion: A male individual always inherits haemophilia from his mother. Reason (R): The gene for haemophilia lies on…1 mkasked 2×
- Q15Assertion: 'Saheli', an oral contraceptive inhibits ovulation and increases phagocytosis of sperms. Reason (R): It is a…1 mkasked 3×
- Q16Assertion: A piece of DNA inserted into an alien organism generally does not replicate, if not inserted into a…1 mkasked 3×
- 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 mkasked 3×
- 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 mkasked 2×
- Q16Assertion: In humans, filariasis is characteried by inflammation in the lower limbs. Reason (R): Filarial worm usually…1 mkasked 2×
- Q16Assertion: Restriction endonuclease recognises palindromic sequence in DNA and cuts them. Reason (R): Palindromic…1 mkasked 2×
- Q16Assertion: When the two genes in a dihybrid cross are situated on the same chromosome, the proportion of parental gene…1 mkasked 2×
- 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 mkasked 3×
- 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 mkasked 3×
- Q17Study the given molecular structure of double-stranded polynucleotide chain of DNA and answer the questions that…2 mkasked 3×
- Q17Student to attempt either option- or: How are morphine and heroin related? Mention their effect on the human body. OR…2 mkasked 3×
- Q17Explain how the immunity of a person is affected if there is atrophy (degeneration) of the thymus gland at an early…2 mkasked 3×
- Q17The basic scheme of the essential steps involved in the process of recombinant DNA technology is summarised below in…2 mkasked 3×
- 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 mkasked 3×
- 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 mkasked 2×
- Q18Student to attempt either option- or: Analyse the following ecosystems and discuss, which will be more productive in…2 mkasked 3×
- Q18"A fully developed foetus initiates its delivery from the mother's womb." Explain. OR Give reasons for the following:…2 mkasked 3×
- 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 mkasked 3×
- Q19Student to attempt either option or. Describe any two situations where a medical doctor would recommend injection of a…2 mkasked 3×
- Q19Explain what is meant by the term amniocentesis. How is this technique misused in India? OR Name any two VDs which…2 mkasked 3×
- Q19A few stages and their respective time period in the evolutionary history of human beings are mentioned in the…2 mkasked 3×
- 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 mkasked 3×
- 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 mkasked 2×
- Q20The basic scheme of the essential steps involved in the process of recombinant DNA technology is summarised below in…2 mkasked 3×
- Q20The basic scheme of the essential steps involved in the process of recombinant DNA technology is summarized below in…2 mkasked 3×
- 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 mkasked 2×
- 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 mkasked 2×
- 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 mkasked 2×
- 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 mkasked 3×
- Q21Explain how the interaction between sea anemone and clownfish is one of the best examples of commensalism in nature. OR…2 mkasked 3×
- 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 mkasked 3×
- 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 mkasked 3×
- Q22Explain the process of formation of placenta in a human female after the implantation of the blastocyst in the…3 mkasked 3×
- Q22Flowering plants with hermaphrodite flowers have developed many reproductive strategies to ensure cross-pollination.…3 mkasked 3×
- 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 mkasked 3×
- 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 mkasked 2×
- Q22A village health worker was taking a session with women. She tells them that one has to be careful while using oral…3 mkasked 3×
- Q23List two reasons that make copper releasing IUDs as effective contraceptives. Explain how the intake of oral…3 mkasked 2×
- Q23"The process of evolution of different species in a given geographical area starts from a point and literally radiates…3 mkasked 3×
- 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 mkasked 3×
- Q23Study the diagram above and answer the following questions: How many alleles are involved in blood grouping? A person…3 mkasked 3×
- 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 mkasked 3×
- 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 mkasked 3×
- 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 mkasked 3×
- Q25Given below is a flower with its characteristic features specialised for the most common type of abiotic pollination.…3 mkasked 3×
- Q25Study a part of life cycle of Plasmodium given below: Answer the following questions: Name the infective stage of…3 mkasked 3×
- Q25Study the given below single strand of deoxyribonucleic acid depicted in the form of a "stick" diagram with 5' - 3' end…3 mkasked 3×
- Q25A person is suffering from high grade fever. Which symptoms will help to identify if he/she is suffering from Typhoid,…3 mkasked 3×
- Q25How does the process of Natural Selection affect Hardy-Weinberg equilibrium? Explain with the help of graphs.3 mkasked 3×
- Q25Enlist three advantages of genetically modified plants.3 mkasked 3×
- Q25Explain the biological treatment of primary effluent when passed into the large aeration tanks in a sewage treatment…3 mkasked 3×
- 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 mkasked 2×
- Q26Name and explain the role of inner and middle walls of the human female uterus. Write the location and function of…3 mkasked 3×
- Q26Why are transgenic animals so called? With the help of an example each, explain the role of transgenic animals in the…3 mkasked 2×
- Q26Samples of blood and urine of a sportsperson are collected before any sports event for drug tests. Why there is a need…3 mkasked 3×
- 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 mkasked 3×
- Q27The insulin synthesised in our body is different from that synthesised by Eli Lilly company using recombinant DNA…3 mkasked 2×
- Q27What do you mean by activated sludge in an STP? Explain the biological treatment of the major part of the sludge…3 mkasked 3×
- Q27Mention any two advantages of micropropagation techniques. Write in brief how the process is carried out in the…3 mkasked 2×
- 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 mkasked 3×
- 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 mkasked 3×
- 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 mkasked 3×
- Q28Name the type of food chains responsible for the flow of larger fraction of energy in an aquatic ecosystem and a…3 mkasked 3×
- 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 mkasked 2×
- Q28Explain the beneficial role of the following, produced as a result of the processes of biotechnology, to mankind: Cow…3 mkasked 3×
- Q28Compare and contrast convergent and divergent evolution.3 mkasked 3×
- Q28Enlist one advantage and two disadvantages of green revolution.3 mkasked 3×
- Q29Highly conserved proteins such as Haemoglobin and Cytochrome-C provide the best biochemical evidences to trace…4 mkasked 3×
- Q29Study the figure given below and answer the questions that follow. Identify the figure and state its importance. Why is…4 mkasked 3×
- 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 mkasked 3×
- Q29Immunity in our body is of two types: (i) Innate immunity and (ii) acquired immunity. Innate immunity is a non-specific…4 mkasked 3×
- Q29Read the following passage and answer the questions that follow. The most convincing evidence to trace evolutionary…4 mkasked 3×
- Q29Read the following passage and answer the questions that follow. According to evolutionary theory, every evolutionary…4 mkasked 3×
- Q30Read the following passage and answer the questions that follow. Deaths related to the use of drugs were estimated at…4 mkasked 2×
- Q30Read the following passage and answer the questions that follow: In nature, we rarely find isolated, single individuals…4 mkasked 3×
- Q30The following question is based on pollination. Study the figures carefully and answer the questions that follow.…4 mkasked 3×
- Q30In 2021, 5 · 3 percent of 15 to 16-year-olds worldwide ( 13 · 5 million individuals) had used Cannabis in the past year…4 mkasked 3×
- Q30Read the following passage and answer the questions that follow. Prevention is the frontline response to drug use.…4 mkasked 2×
- Q30The process of copying the genetic information from one strand of DNA into RNA is termed as transcription. The…4 mkasked 3×
- 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 mkasked 2×
- Q31(i) Explain how does double fertilisation take place in a flowering plant. (ii) Write the fate of the products of…5 mkasked 3×
- 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 mkasked 2×
- 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 mkasked 3×
- 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 mkasked 3×
- Q32(i) Describe the population growth curve applicable in a population of any species in nature that has unlimited…5 mkasked 3×
- 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 mkasked 3×
- Q33(i) Describe the population growth curve applicable in a population of any species in nature that has limited resources…5 mkasked 3×
- Q33(i) Describe the Species-Area relationship as observed by Alexander von Humboldt, for a wide variety of taxa in nature.…5 mkasked 3×
- Q33Study the given diagram showing the sectional view of a seminiferous tubule. Answer the following questions: (i) Label…5 mkasked 2×
- Q33Student to attempt either option or. (i) Explain giving three reasons why tropics show greatest levels of species…5 mkasked 3×
- 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.