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Class 12th Biology Question Paper CBSE-Group-1

Class 12th Biology Question Paper CBSE-Group-1-Study Matrial


Question Paper (Group I)
Class : XII   Subject  : Biology
Time : 3 Hours                                                                                                 Max. Marks : 70

General Instructions:
All the questions are compulsory.
The question paper consists of four sections A, B, C, and D. Section- A contain 8 questions of 1 mark each, Section-Bcontains 10 questions of 2 marks each, Section-C has 9 questions of 3 marks each and Section-D contains 3 questions of 5 marks each.
There is no overall choice. However, an internal choice has been provided in some questions. A student has to attempt only one of the alternatives in such questions.
Wherever necessary, the diagram drawn should be neat and properly labeled.

Q1. Offsprings produced by asexual reproduction are referred to as clones. Why?
Q2. Why are pollen grains produced in enormous quantity in Maize?
Q3. Name the disorder with the following chromosome complement.
(i) 22 pairs of autosomes + X X Y
(ii) 22 pairs of autosomes + 21st chromosome + XY.
Q4. What is adaptive radiation?
Q5. Name the two major groups of cells required to attain specific immunity
Q6. Some enzymes are used to cut DNA into fragements. These are considered as molecular scissors. What is the name assigned to such enzymes?

Q7. Name two commonly used vectors in genetic engineering
Q8.  Who are generally the pioneer species in a Xerarch succession and in a Hyararch succession?
Q9. Give the function of:-
(a) Corpus luteum (b) Endometrium
Q10.  Expand: 1) GIFT   2) ZIFT   3) IVF     4) IUT

Q11. Complete the blanks a, b, c and d on the basis of Frederick Griffith Experiment.
S Strain inject into mice (a)
R strain inject into mice (b)
S strain (heat killed) inject into mice  (c)
S strain (heat killed) + R strain (live) inject into mice  (d)
Q12.  A woman with O blood group marries a man with AB blood group
(I) work out all the possible phenotypes(II) genotypes of the progeny
Q13.  Given below are the pathogens and the diseases caused by them. Which out of these pairs is not correct matching pair and why?
(a) Wuchereria– --------------- Filariasis
(b) Microsporum–--------------Ringworm
(c) Salmonella –---------------- Common Cold
(d) Plasmodium – --------------Malaria
Q14. Explain with reference to PCR: A specific enzyme helps in amplification in PCR. Name the bacterium from which it is isolated and state how its thermostable nature is helpful.
Q15.  Differentiate between stenohaline and euryhaline organisms.
Q16. Differentiate between primary succession and secondary succession.Which one occurs      faster?
Q17.  An ecologist wants to explore an area with a higher biodiversity. Suggestwhether he/she should explore a tropical region or a temperate region?Why?

Q18. Catalytic converters use expensive metals as catalysts.
(a) Name the metals generally used.
(b) What precaution should be observed while using catalytic converter.
Q19.  Continued self pollination lead to inbreeding depression. List three devices, which flowering plant have developed to discourage self pollination?

Q20. Mention the name and role of hormones which are involved in regulation of gamete formation in human male

Q21.  What is a point mutation? Explain  with one example?
Q22.  Name the three major types of RNAs, specifying the function of each in the synthesis of Polypeptide.
Q23.  (i)  State the Hardy-Weinberg principle.
(ii)  When there is a disturbance in the Hardy-Weinberg equilibrium, what would it result in?
         (iii)  According to this principle, what is the sum total of all allelic frequencies
Q24.  Municipal Corporation has deputed personnel to check for mosquito breeding in your school.
(a) Which are the places they should check for mosquitoes and their larvae?
(b) Name to diseases which are spread by mosquitoes.
(c) Name any two biological agents which can be used to control mosquitoes
(d)   What values it shows?
Anand a 14 yr old boy thinks smoking makes him more energetic and feel like adult and thusmoreresponsible citizen. He tries to smoke when he is with his peer group. As a friend you haveto educate him
(a) Why he feels more energetic while smoking?
(b) Effects of CO in smoke 
(c) Other ill effects on body
(d) Which values are shown by the friend by educating him for not smoking?
Q25.  The immune system of a person is suppressed. He was found positive for a pathogen in the
          Diagnostic test ELISA.
(a) Name the disease, the patient is suffering from.
(b) Which pathogen is identified by ELISA test?
(c) Which cells of the body are attacked by the pathogen?

Q26.  Biofortification is the most practical means to improve public health. Justify the statement with examples.

Q27.  What is meant by germplasm Collection? Describe its significance in plant breeding                 programmes


Q28.  Describe the various steps involved in the technique of DNA fingerprinting
Answer the following questions based on messelson and stahl experiment.

a) Why did the scientists used 15NH4Cl and 14NH4Cl as sources of Nitrogen in the Culture medium for growing 15N got incorporated into?
b) Name the molecules that 15N got incorporated into?
c) How did they distinguish between 15N labeled molecules from 15N ones?
d) Mention the significance of taking E-coli samples at definite time intervals for observations?
e) Write the conclusion drawn by them at the end of their experiment.
Q29.  The clinical gene therapy is given to a 4 years old patient for an enzyme which is crucial for the Immune system to function.

  A  Lymphocytes of the patient.
  B    -------------------------------

  C   Introduction of functional ADA cDNA into lymphocytes

  D    -----------------------------

Observe the therapeutical flow chart and give the answer of the following :
a) Complete the missing steps (B) and (D)
b) Identify the disease to be cured.
c) Why the above method is not a complete solution to the problem?
d) Scientists have developed a method to cure this disease permanently. How?

Q30.  Describe at least two approaches each for ex-situ conservation and in situ conservation as a Strategy for biodiversity conservation.
Pollutant from man’s activities like effluents from industries and homes can radically accelerate the ageing process.
(a) Explain how does this process occurs during natural ageing of lake.
(b) Give the term used for accelerated ageing of water bodies. Also give the term used for the natural ageing of lake.



Ans 1.  Because offsprings produced by Asexual reproduction is morphologically and genetically        identical to parent.                                                                                                               1
Ans 2.   To ensure pollination because Maize is pollinated by wind                                 1
Ans 3.   (i) Klinefetter’s Syndrome (ii) Down’s syndrome                                                  ½+½=1
Ans 4.    Adaptive radiation : The process of evolution of different species in a geographical area starting   from a point and literally radiating to other habitats is called adaptive radiation.             1
Ans 5.    B-lymphocytes and T-lymphocytes                    ½+½=1
Ans 6.    Restriction Enzymes.         1
Ans 7.    Plasmid and Bacteriophage.              ½+½=1
Ans 8.    Pioneer species in Hydrarch succession are usually the small phytoplanktons and that in Xerarch succession are usually lichens.                                                            ½+½=1


Ans 9.  Corpus luteum :It secretes progesterone which prepares endometrium of uterus for implantation and normal development of foetus.
Endometrium :It undergoes cyclic changes during menstrual cycle and prepares itself for implantation of blastocyst.     1+1

Ans 10.  (1)  Gamete intra fallopian transfer (GIFT
        (2) IVF :In Vitro Fertilisation
 (3) ZIFT :Zygote Intra Fallopian Transfer
      (4) IUT :Intra Uterine Transfer –              ½ X 4=2

Ans 11.    (a) Mice die
     (b) mice live
     (c) mice live
     (d) mice die                       ½ X 4=2

Ans 12.  (I)  Blood group AB has alleles as IA, IB and O group has ii which on cross gives the both blood groups A and B 
      II)  The genotype of progeny will be IAi and IBi.        1+1

Ans 13.  Salmonella :Common cold is not a matching pair.
    Salmonella causes typhoid.              1+1

Ans 14.   Taqpolymerase obtained from bacterium called as Thermus aquaticus.         1+1

Ans 15.   Euryhaline :Organisms tolerant in wide range of salinities.
   Stenohaline :Organisms tolerant to narrow range of salinities            1+1
Ans 16.  Primary Succession : A process that starts where no living organisms are there.
      Secondary succession :A process that starts in areas which have lost all the living organisms that existed there.            1+1

Ans 17.   He should explore tropical region because tropical regions have higher diversity due to:
    (i) More speciations as remained undisturbed for millions of year.
    (ii) Less seasonal so more niche specialisation for species.
    (iii) More solar energy so more productivity.        1+1

Ans 18.  (a) Catalysts : platinum - palladium and Rhodium
   (b) Motor vehicles equipped with catalytic converters should use unleaded petrol as lead inactivates the catalysts.            1+1  


Ans 19.   (a) Release of pollen and stigma receptivity is not synchronised in some species
 (b) Anther and stigma are at different position/heights in some plants
 (c) Self-incompatibility. 1X3=3

Ans 20. The increased   levels of GnRH then acts at the anterior pituitary gland and stimulates secretion of     two gonadotropins – luteinising hormone (LH) and follicle stimulating hormone (FSH). LH acts at the   Leydig cells and stimulates synthesis and secretion of androgens. Androgens, in turn, stimulate the   process of spermatogenesis. FSH acts on the Sertoli cells and stimulates secretion of some factors which   help in the process of spermiogenesis.               3
Ans 21.    A  mutation that arises due to change in a single base pair of DNA 
Example: In sickle cell anemia the problem arises due to a point mutation in the gene that  codes for Beta polypeptide. Due to this mutation the amino acid glutamic acid at the position no. 6 is replaced by amino acid valine        1+2=3
Ans 22.   (i) mRNA-(Messenger RNA) :decides the sequence of amino acids.
    (ii) tRNA-(Transfer RNA) : (a) Recognises the codon on mRNA 
    (b) transport the aminoacid to the site of protein synthesis.
    (iii) rRNA (Ribosomal RNA) : Plays the structural and catalytic role during translation.       1X3=3
Ans 23.   (i) The allele frequency in a population are stable and constant from generation to generation.
    (ii) Evolution.
    (iii) One.        1X3=3

Ans 24.   a) Water tanks , flowerpots, stagnant water
 b)  Dengue, Malaria
 c) Gambusia, dragonfly
 d) Values
    • Observation
    • Sensitivity towards health.   2+1=3
(a) He fells energetic because nicotine raises blood pressure and increases heart beat. This is not good for his health.
(b) CO binds to hemoglobin and reduces concentration of oxygen
(c) Any one effort cancer of lung, throat, emphysema.
(d)  Values
• Awareness about health
• Consciousness.
• Critical thinking.        2+1=3

Ans 25.   (i) AIDS (Acquired Immuno Deficiency Syndrome)
    (ii) HIV (Human Immunodeficiency Virus)
    (iii) Helper T-cells, macrophages, B-lymphocytes.         1X3=3

Ans 26. Biofortification is the plant breeding programme designed to increase Vitamins, minerals, heigher proteins and healthier fat content in crops. This programme improves the quality of food products. It is required to prevent hidden hunger. Some of the examples of fortified crops are:

    (i)  New hybrid of maize : had twice the amount of amino acid lysine and tryptophan.
    (ii) Wheat : Atlas 66, having a high protein content.
    (iii) Rice : 5 times iron than the normal amount. IARI Delhi has released several crops which are rich in vitamins and minerals. Consumption of such biofortified food will vastly improve the  public health.            1+2=3

Ans 27. The collection of all the diverse alleles of all the genes of crop plant is called germ plasm collection.
  In plant breeding programmes, the germplasm provides the entire of genes and alleles, and the characterstics which they express. The plant breeders select the most favourable characters of a particular gene and manipulate its transfer to a desirable parent.           1+2=3


Ans 28.     Steps/procedure in DNA fingerprinting –
Extraction of DNA - using high speed refrigerated centrifuge.
Amplification - many copies are made using PCR
Restriction Digestion - using restriction enzymes DNA is cut into fragments.
Separation of DNA fragments - using electrophoresis-agarose polymer gel.
Southern Blotting : Separated DNA sequences are transferred onto nitrocellulose or nylon membrane.– Hybridisation : The nylon membrane exposed to radio active probes.
Autoradiography : The dark bands develop at the probe site.                                     1X5=5
a. Nitrogen got incorporated into newly synthesized DNA.
b. DNA, Proteins, nucleic acid
c. Based on centrifugation in cesium chloride…..
d. To study the cells as they multiplied and extracted DNA that remained as helices
e. Page – 105, Point (iii) – DNA replication is semiconservative 1X5=5

Ans 29.   (a) Step (B) : Lymphocytes are grown in culture medium.
                Step (D) : Infusion of genetically engineered lymphocytes into patients.
(b) Adenosine deaminase (ADA) deficiency.
(c) As genetically engineered lymphocytes are not immortal, the patient requires periodic infusion of cells.
(d) If the gene isolated from bone marrow cells producing ADA is introduced into cells at early embryonic stages, it could be a permanent cure.                    1X5=5

Ans 30.  In situ conservation :
(i) Identification and maximum protection of ‘hot spots’
(ii) Legal protection to ecologically rich areas.
(iii) Biosphere reserves, national parks and sanctuaries
(iv) Sacred groves.
 Ex situ Conservation :
(i) Creation of zoological parks, botanical garden, wild life sanctuary
(ii) Cryopreservation
(iii) Seed bank     3+2=5
(a) The phenomeon is eutrophication. More nutrients in water, aquatic life increases organic remains deposited on lake bottom, lake grows shallower and warmer, gradually transforms into land due to deposition of silt and organic debris.
(b) Cultural or Accelerated eutrophication
Natural ageing is Eutrophication.               2.5+2.5=5

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