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CBSE XII Pre Boards 2015 : BIOLOGY with Answers (KV Chennai)

7 pages, 44 questions, 15 questions with responses, 19 total responses,

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KENDRIYA VIDYALAYA SANGATHAN CHENNAI REGION CLASS XII COMMON PRE BOARD EXAMINATION 2014-2015 Subject :Biology Time Allotted: 3 hrs Max .Marks : 70 General Instructions: (i) All questions are compulsory. (ii ) This question paper consists of four Sections A, B, C and D.Section A contains 5 questions of one mark each, Section B is of 5 questions of two marks each, Section C is of 12 questions of 3 marks each and a VBQ of 4 mark, Section D is of 3 questions of five marks each. (iii) There is no overall choice. However, an internal choice has been provided in one question of 2 marks, one question of 3 marks and all the three questions of 5 marks weightage. A student has to attempt only one of the alternatives in such questions. (iv) Wherever necessary, the diagrams drawn should be neat and properly labelled. SECTION: A 1. What does the term dioecious denote in plants? 1 2. In a dihybrid cross, when would the proportion of parental gene combinations be much higher than non-parental types as experimentally shown by Morgan? 1 3. What is biopiracy? 1 4. Name the amino acids having only one codon. 1 5. What is the role of Morphine in the patients those who have undergone surgery? 1 SECTION: B 6. IARI has released several varieties of crop plants that are biofortified .Give two examples of such crops and their biofortification. 2 7. In several species such as papaya, male and female flowers are present on different plants. What are the types of pollination prevented by this condition? 2 8. What are UTRs in mRNA? What is its role? 2 9. What is interspecific hybridization? Give an example. 2 10. Mention how e-waste is produced and disposed of.What is the solution for this problem? OR What are sacred groves? Mention the sacred groves in Rajasthan and Meghalaya. 2 SECTION: C 11. What are the advantages offered by seeds to angiosperms? 3 12. Name the three layers of tissues which form the wall of the uterus .Write its role. 3 13. A pregnant human female was advised to undergo MTP.It was diagnosed by the doctor that the fetus she is carrying has developed from a zygote formed by an XX egg fertilized by Y-carrying sperm. Why was she advised to undergo MTP? 3 Page 1 of 3 14. a) Explain the mechanism of inheritance of colour blindness. b) A woman with normal vision, whose father is colour blind, marries a normal vision man. What will be the phenotype of their progeny? Draw a pedigree chart. 15. What are the three different ways in which natural selection can affect the frequency of a heritable trait in a population? Explain. 3 16. Trace the events that occur in human body to cause immunodeficiency when HIV gains entry into the body. OR Early detection of cancer allows the disease to be treated successfully .Explain the various diagnostic techniques for cancer. 3 17. What is protoplast? Describe the steps involved in somatic hybridization. 3 18. Explain the biogas formation in a biogas plant. 3 19. With the help of diagrammatic representation only, show the steps of recombinant DNA technology. 3 20. Gene therapy allows the correction of a gene defect .Explain the first clinical gene therapy. 3 21. Name and explain the technique used in the separation and isolation of DNA fragments to be used in recombinant DNA technology. 3 22. If the stressful external conditions are localized or remain only for a short duration, what are the two other alternatives for the organisms to escape from stressful conditions? 3 23. Solid wastes are becoming a great menace nowadays in the urban cities especially of plastics. States across the country are trying to push for reduction in use of plastics. a) What is your role in this aspect? b) How can you reduce the usage of plastics? c) What is your opinion of future without plastics? d) Why plastics are considered to be a great menace? 4 SECTION: D 24. a) Label the parts A to F of the figure given below .What is the fate of C after fertilization. b) Why does a pollen grain possess two male gametes? Explain. Page 2 of 3 OR a) Draw a diagrammatic sectional view of ovary. b) Name the structure that secretes progesterone .Where is that structure present? How is it formed? c) What is the role of progesterone? 5 25. a) Explain the process of aminoacylation of tRNA . b) How do ribosomes act as cellular factory responsible for synthesizing proteins? c) Describe initiation and termination phases of protein synthesis. OR a) Explain how the inheritance pattern of hemophilia and sickle cell anemia differ from each other. b) Write the symptoms of hemophilia and sickle cell anemia in human. 5 26. a) Name and explain the kind of interaction in the following i) Algae and fungi in Lichens ii)Head louse and human iii) Clown fish and Sea anemone. b) What is brood parasitism explain with an example. OR Explain the salient features of sedimentary cycle in an ecosystem. How does it differ from gaseous cycle in an ecosystem? 5 ************************************************************************* Page 3 of 3 KENDRIYA VIDYALAYA SANGATHAN CHENNAI REGION CLASS XII COMMON PRE-BOARD EXAMINATION 2014-2015 BIOLOGY Time: 3 Hours Max. Marks: 70 Answer Key S.No . 1 2 3 4 5 6 7 8 9 10 OR 11 12 13 XII BIO Value points Unisexual Genes are linked Use of bio-resources by multinational companies and other organizations without proper authorization from the countries and people concerned without compensatory payment Methionine tryptophan( try) Sedative and pain killer IARI - The Indian Agricultural Research Institute, New Delhi e.g.1. vitaminA enriched carrots, spinach, pumpkin; 2. vitamin C enriched bitter gourd, bathua, mustard, tomato; 3. iron and calcium enriched spinach and bathua; and protein enriched beans broad, lablab, French and garden peas.( any two) Autogamy and geitenogamy Untranslated region in mRNA, efficient translation process Crossing between two different species ,mule Irreparable computers and other electronic goods ,buried in land fills or incinerated , recycling is the only solution Tracts of forest were set aside and all the trees and wildlife within were venerated and given total protection Khasi and Jaintia hills in Meghalaya Aravalli hills of Rajasthan Reproductive processes such as pollination and fertilization are independent of water ,seed formation is more dependable . Dispersal to new habitats colonise in other areas Sufficient food reserves young seedlings are nourished /hardseed coat give protection Perimetrium, external thin membranous layer , Myometrium, strong contraction during child birth , Endometrium, cyclic changes takes place Klinefelter s Syndrome (Child will be born with) overall masculine development , Gynaecomastia , sterile PREBOARD Mark s 1 1 x2 x2 x2 1x2 1 x2 1+1 1+1 1+1/2 x2 1+ `1/2 x2 1x3 1x3 1 x3 Page 1 of 4 14 1 Sex linked recessive disorder males are more prone to this disorder follow criss cross inheritance Colour blind father= XCY Normal vision daughter but carrier = XXC Marries a normal man = XY Phenotype of the progegy X Y XX XY X Normal Normal Female Male C XX XCY XC 15 16 OR 17 18 Carrier Female Normal vision 2 Colour blind man Stabilising (medium sized are favoured), Directional( Shifts to one direction), Disruptive ( two peaks ) HIV enters macrophages ,RNA genome form viral DNA reverse transcriptase,incorporated into host DNA,viral particles produced,enter helper T cells ,decrease cells/ immune deficiency Biopsy and histopathological studies of tissue and blood , bone marrow test , radiography, CT MRI of internal organs , Antibodies against cancer-specific antigens, techniques of molecular biology Surrounded by plasma membrane ,isolated protoplasts with desired character fused to get hybrid protoplasts grown to form new plant somatic hybrids ,somatic hybridisation Concrete tank in which bio wastes are collected and slurry of dung is fed a floating cover over the slurry keeps rising as the gas is produced the tank biogas has an outlet which is connected to a pipe to supply biogas 19 1x 3 x6 x 6 1x3 1x3 1x3 Foreign DNA and Vector DNA cut by same restriction enzyme ,Ligases join foreign DNA to plasmid r DNA transformation cells divide( diagrammatic representation ) XII BIO PREBOARD Page 2 of 4 20 21 22 23 24 ADA deficiency crucial for immune system ,due to deletion of gene for the enzyme, ADA c DNA using retrovirus introduced into lymphocytes returned to patients cells are not immortal periodic infusion is essential Fragments are separated by gel electrophoresis, DNA negatively charged move towards anode under an electric current ,agarose gel is a natural polymer ,visualized after staining with ethidium bromide ,exposure to UV orange coloured bands ,elution Migrate (Siberian birds ) to Rajasthan ,Suspend- dormancy of seeds spores hibernation ,aestivation ,diapause i)Use of ecofriendly packaging , ii) carry cloth or other natural fibre carry bags iii) refusing polythene bags iv)non biodegradable ( any other value points) a)A- antipodal B- polar nuclei C- central cell D-egg E-synergids F-filiform apparatus / into endosperm b) double fertilization /one fuses with egg another fuses with fused polar nuclei OR Maintenance of endometrium OR 26 XII BIO x 6 x 6 1x4 3 1 x2 2 Corpus luteum in the ovary , follicle after ovulation transformed into corpus luteum 25 x 6 a)aminoacids are activated in the presence of ATP linked to tRNA b)small subunit encounter m RNA translation begins ,two sites of large unit aminoacids bind peptide bond formation c)start codon AUG initiation tRNA , release factor binds to stop codon terminating translation Haemophilia sexlinked recessive , sickle cell anemia- autosomal recessive , Haemophilia-single cell protein in the cascade of proteins is affected . males are more prone than females in haemophilia Sickle cell anemia-HbA Hbs carriers substitution of glutamic acid by valine substitution in 6th codon A simple cut result in Non-stop bleeding,mutant haemoglobin undergo polymerization under low oxygen tension causing change in the shape of the rBC from biconcave to elongated sickle shape i)Mutualism algae photosynthetic partner fungi absorb water and minerals PREBOARD 2 1 1 2 2 1 2 2 3 Page 3 of 4 OR XII BIO ii)Parasitism on human ,parasite derive nutrient from host iii)Commensalism protected from predator due to stinging cells Parasitic bird lays its eggs in the nest of its host and let the host incubate them .eggs resemble the host s egg in size and colour The natural reservoir is rock ,contain in the form of phosphates . When rocks are weathered minute amounts of these dissolve in soil solution and are absorbed by the roots of the palnts ,harbivores and other animals obtain from plants , wastes are decomposed by phosphate-solubilising bacteria releasing phosphorus Atmospheric inputs of phosphorus throughrainfall are much small;ler than carbon inputs, gaseous exchanges of phosphorus between organism and envi. are negligible PREBOARD 2 x6 2 Page 4 of 4

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