
	Trending ▼ ICSE CBSE 10th ISC CBSE 12th CTET GATE UGC NET Vestibulares ResFinder

CBSE Class 12 Pre Board 2021 : Biology - Set 1 (CBSE Gulf Sahodaya Qatar Chapter, Doha)

10 pages, 112 questions, 0 questions with responses, 0 total responses,

	CBSE 12 Pre Boards	+Fave Message
	Profile Timeline Uploads

Home > cbse12_pre_boards > F Also featured on: School Page cbse12

Formatting page ...

Pre Board Examination, 2020-21 Subject - Biology (044) Class 12 Date: Time Allowed: 3 hours Max. Marks: 70 General Instructions: 1. 2. 3. 4. 5. 6. General Instructions: All questions are compulsory. The question paper has four sections: Section A, Section B, Section C and Section D. There are 33 questions in the question paper. Section A has 14 questions of 1 mark each and 02 case-based questions of 4 marks each. Section B has 9 questions of 2 marks each. Section C has 5 questions of 3 marks each and Section D has 3 questions of 5 marks each. There is no overall choice. However, internal choices have been provided in some questions. A student has to attempt only one of the alternatives in such questions. Wherever necessary, neat and properly labelled diagrams should be drawn. SECTION A 1. Mention the pollinating agent of an inflorescence of small dull coloured flowers with (1) well exposed stamens and large feathery stigma. Give any one characteristic of pollen grains produced by such flowers. 2. Why is the enzyme cellulase needed for isolating genetic material from plant cells and (1) not from animal cells? 3. How many meiotic divisions are required to produce 100 seeds of tomato. (1) 4. Name one trait in humans which follows the same pattern of inheritance as the eye (1) colour of Drosophila. 5. An anther with malfunctioning tapetum often fails to produce viable male (1) gametophytes. Give any one reason. 6. What was the speciality of milk produced by the transgenic cow Rosie? Page 1 of 10 (1) 7. The egg of an animal contains 10 chromosomes, of which 1 is X chromosome. How (1) many autosomes would be there in the karyotype of this animal? 8. What is corpus luteum? (1) 9. What are true breeding lines that are used to study the inheritance pattern of traits in (1) plants? 10. Why is oxytocin called as birth hormone ? (1) 11. Assertion: Endosperm is a nutritive tissue and it is triploid. (1) Reason: Endosperm is formed by the fusion of the secondary nucleus to the second male gamete. It is used by the developing embryo. a. Both assertion and reason are true, and reason is the correct explanation of assertion. b. Both assertion and reason are true, but reason is not the correct explanation of assertion. c. Assertion is true but reason is false. d. Both assertion and reason are false. OR Assertion: Ovule develops into mature seeds and ovary develops into fruits. Reason: The fruits that develop from only ovary are called true fruits. a. Both assertion and reason are true, and reason is the correct explanation of assertion. b. Both assertion and reason are true, but reason is not the correct explanation of assertion. c. Assertion is true but reason is false. d. Both assertion and reason are false. 12. Assertion: In Griffith s experiment mice were injected by a mixture of heat killed Smooth type bacteria and live Rough type bacteria. Some mice died of pneumonia and their blood contained both live Rough type bacteria and live Smooth type bacteria. Reason: The dead Smooth type bacteria became alive and caused pneumonia. Griffith named it as transforming principle. a. Both assertion and reason are true, and reason is the correct explanation of assertion. Page 2 of 10 (1) b. Both assertion and reason are true, but reason is not the correct explanation of assertion. c. Assertion is true but reason is false. d. Both assertion and reason are false. 13. Assertion: The size of morula is the same as that of the zygote. (1) Reason: Zona pellucida remains intact till cleavage is completed. a. Both assertion and reason are true, and reason is the correct explanation of assertion. b. Both assertion and reason are true, but reason is not the correct explanation of assertion. c. Assertion is true but reason is false. d. Both assertion and reason are false. 14. Assertion: Central dogma is the flow of information from DNA to mRNA and then (1) decoding the information present in mRNA in the form of protein. Reason: In retroviruses reverse of central dogma occurs. a. Both assertion and reason are true, and reason is the correct explanation of assertion. b. Both assertion and reason are true, but reason is not the correct explanation of assertion. c. Assertion is true but reason is false. d. Both assertion and reason are false. 15. Read the following and answer any four questions from 15(i) to 15(v) given below: Page 3 of 10 (4x1=4) Microsoft Word - Trends-World-Contraceptive-Use-2015_formats-updated20160224.do i) What is the function of copper-T? (a) stops obliteration of the blastocoel (b) checks mutation (c) stops fertilization (d) stops zygote formation ii) The success of birth control programme in controlling population growth is dependent on (a) tubectomy (b) use of contraceptives (c) vasectomy (d) acceptability of the above by the people iii) Which one of the following is tested by the technique of amniocentesis? (a) chromosomal abnormalities in a foetus (b) biochemical abnormalities in a foetus (c) errors of metabolism in a foetus (d) all the above Page 4 of 10 iv) Test tube baby means a baby born when (a) developed in a test tube (b) ovum is fertilized externally and thereafter implanted in the uterus (c) it is developed through the tissue culture method (d) developed from a non-fertilized egg v) The woman starts taking the birth control pills on about day ________ of the menstrual cycle. (a) (b) (c) (d) 1 day 5 days 10 days 14 days OR 16. What do male condoms condoms offer that other forms of birth control do not? (a) least chance of failure (b) best protection against sexually transmitted infections (STIs) (c) cheapest to use (d) all of the above Read the following and answer any four questions from 16(i) to 16(v) given below: Page 5 of 10 (4x1=4) i) In the above pedigree, find out of the following four: (a) Autosomal dominant (b) Autosomal recessive (c) X linked dominant (d) X linked recessive ii) A pedigree is shown below for a disease that is autosomal dominant. The genetic makeup of the first generation is: (a) AA, Aa (b) Aa. aa (c) Aa. AA (d) Aa, Aa Page 6 of 10 iii) Given below is a pedigree chart of a family with five children. It shows the inheritance of attached earlobes as opposed to the free ones. Which one of the following conclusions drawn is correct? (a) The parents are homozygous recessive (b) The trait is Y linked (c) The parents are homozygous dominant (d) The parents are heterozygous iv) What does the pedigree below conclude? (a) autosomal dominant (b) autosomal recessive (c) X- linked dominant (d) X linked recessive v) Given below is a pedigree chart showing the inheritance of a certain sex-linked trait in humans The trait traced in the above pedigree chart is (a) Dominant X-linked (b) Recessive X-linked (c) Dominant Y-linked (d) Recessive Y-linked Page 7 of 10 SECTION B Question numbers 17 to 25 carry two marks each. 17. How has the fungus, Trichoderma polysporum proved to be very essential to organ- (2) transplant patients? 18. Differentiate between rDNA and cDNA. (2) 19. Draw and label any three parts of an anatropous ovule. (2) 20. What are the problems faced by a sickle cell anaemia carrier? Why is this defective (2) gene still not eliminated by nature? 21. How is gene therapy being used in treating ADA deficient patients? (2) 22. Differentiate between sertoli and leydig cells. (2) OR Mention the sites of action of the hormones GnRH and FSH during spermatogenesis in human males. Give one function for each of the hormones. 23. AUGGACCUGAUAUUUUGA is the base sequence in a strand of mRNA. (2) (i) Write the base sequence of the DNA strand from which it has been transcribed. (ii) Upon translation, how many amino acids will the resulting peptide have? 24. How is IUT different from ZIFT? (2) 25. A tRNA is charged with the amino acid phenylalanine. (2) (i) At what site of the ribosome will the tRNA bind? (ii) At what end of the tRNA is the amino acid attached? (iii) What is the mRNA codon for phenylalanine? (iv) Name the enzyme responsible for this binding? SECTION-C Question numbers 26 to 30 carry three marks each: 26. With the help of flow charts/ diagrams differentiate between spermatogenesis and oogenesis. OR Page 8 of 10 [3] Describe the post zygotic events leading to implantation and placenta formation in humans. Mention any two functions of placenta. 27. Given below is a table showing the genotypes and the phenotypes of blood groups in the human population. S. No. Genotype Phenotype 1. (W) A 2. IBi (Y) 3. IAIB (Z) 4. (X) O [3] (i) Identify the Genotypes W and X and Phenotypes Y and Z. (ii) How is co-dominance different from incomplete dominance and dominance? 28. How do ori and cloning sites facilitate cloning into vector? [3] 29. Apart from being a part of the food chain, predators play other important roles. [3] Mention any two such roles supported by examples. 30. What is the role of each of the following in the body defences? (i) Antihistamine (ii) Plasma cells [3] (iii) Helper T cells SECTION - D Question numbers 31 to 33 carry five marks each. 31. One of the main objectives of biotechnology is to minimise the use of insecticides on [5] cultivated crops. Explain with the help of a suitable example how insect resistant crops have been developed using techniques of Biotechnology. OR Describe by diagrammatic representation the process of recombinant DNA technology. 32. DNA molecule in human chromosome 1 has 2968 genes. On an average each gene consists of 3000 bases. Explain how such a long DNA molecule is packed within the chromosome. OR Page 9 of 10 [5] A true breeding pea plant homozygous for axial violet flowers is crossed with another pea plant with terminal white flowers. (i) What would be the phenotype and genotype of F1 and F2 generations? (ii) Give the phenotypic ratio of F2 generation. (iii) List the Mendel s generalisations that can be derived from the above cross. 33. (i) Draw a schematic labelled diagram of the vertical section of a maize grain. (ii) Why can we not use the term seed for maize grain? OR (i) Trace the development of megaspore mother cell up to the formation of a matureembryo sac in a flowering plant. (ii) Draw a labelled diagram of the structure of mature dicot embryo. ********************************* * Page 10 of 10 [5]

Formatting page ...

Tags : cbse pre boards, prelims 2015 - 2016, preliminary examinations, central board of secondary education, india schools, free question paper with answers, twelfth standard, xiith std, board exams, mock, model, sample, specimen, past, free guess papers.india, delhi, outside delhi, foreign, cbse class xii, cbse 12, 12th standard, cbse papers, cbse sample papers, cbse books, portal for cbse india, cbse question bank, cbse question papers with answers, pre board exam papers, cbse model test papers, solved board question papers of cbse last year, previous years solved question papers, free online cbse solved question paper, cbse syllabus, india cbse board sample questions papers, last 10 years cbse questions papers, cbse important questions, specimen / mock papers.

cbse12_pre_boards chat

Horizontal lines at:
Guest Horizontal lines at:
AutoRM Data:
Box geometries: