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Name of the Board : CBSE Academic
Class : XII STD
Document Type : Sample Question Paper
Subject : Biology
Paper : Class XII Sample Question Paper 2019-20
Year : 2019-20
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CBSE Class XII Biology Sample Question Paper

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Time Allowed : 3 hours

Related : CBSE Mathematics Sample Question Paper 2019-20 :


1. There are a total of 27 questions and five sections in the question paper. All questions are compulsory.

2. Section A contains question numbers 1 to 5, multiple choice questions of one mark each.
Section B contains question numbers 6 to 12, short answer type I questions of two marks each.
Section C contains question numbers 13 to 21, short answer type II questions of three marks each.
Section D contains question number 22 to 24, case-based short answer type questions of three marks each (1+1+1).
Section E contains question numbers 25 to 27, long answer type questions of five marks each.

3. There is no overall choice in the question paper. However, internal choices are provided in two questions of one mark, one question of two marks, two questions of three marks and all three questions of five marks. An examinee is to attempt any one of the questions out of the two given in the question paper with the same question number.

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Section – A

1. Androgens are synthesized by:
a.) Sertoli Cells
b.) Leydig cells
c.) Seminal vesicles
d.) Bulbourethral gland
A procedure that finds use in testing for genetic disorders, but is also misused
for foeticide is:
a.) Lactational amenorrhea
b.) Amniocentesis
c.) Artificial insemination
d.) Parturition 1

2. Transplantation of tissues/organs to save certain patients often fails due to rejection of such tissues/organs in the patient’s body. Which type of immuneresponse is responsible for such rejection?
a.) auto-immune response
b.) humoral immune response
c.) physiological immune response
d.) cell-mediated immune response

Which of the following are the correct reasons for Rheumatoid arthritis?
i.) Lymphocytes become more active
ii.) Body attacks self cells
iii.) More antibodies are produced in the body
iv.) The ability to differentiate pathogens or foreign molecules from self cells is lost

Choose the correct answer from the options given below:
a.) i and ii
b.) iii and iv
c.) i and iii
d.) ii and iv

3. Name the enzymes ‘P’ and ‘Q’ that carry out the following processes
a.) Enzyme P-Exonuclease and Enzyme Q-Permease
b.) Enzyme P-Exonuclease and Enzyme Q- Ligase
c.) Enzyme P-Endonuclease and Enzyme Q- Permease
d.) Enzyme P-Endonuclease and Enzyme Q-Ligase 1

4. A biotechnologist wanted to create a colony of E.coli possessing the plasmidpBR322, sensitive to Tetracycline. Which one of the following restriction sites would he use to ligate a foreign DNA?
a.) Sal I
b.) Pvu I
c.) EcoRI
d.) Hind III 1

5. Most important cause of biodiversity loss is:
a.) Over exploitation of economic species
b.) Habitat loss and fragmentation
c.) Invasive species
d.) Breakdown of plant-pollinator relationships

Section – B

6. How does an encysted Amoeba reproduce on return of favourable conditions?
What are gemmules and conidia? Name one organism each in which these are formed? 2
7. Name any two copper related IUD’s. Explain how it acts as a contraceptive? 2
8. Why is it not possible to study the inheritance pattern of traits in human beings, the same way as it is done in pea plant? Name the alternate method employed for such an analysis of human traits. 2
9. Carefully examine structures A and B of pentose sugar given below. Which one is more reactive? Give reasons.
10. Name the technology and the procedure involved which can help a scientist recover virus free sugarcane plants from diseased canes for his crop breedingexperiments.

11. Explain the events that occur in the host cell on introduction of nematoderesistant gene into the tobacco plant by using Agrobacterium vectors.2
12. Construct a pyramid of biomass starting with phytoplankton. Label three trophic levels. Is the pyramid upright or inverted? Justify your answer.2

Section – C

13. Draw a well labelled diagram of L.S of a pistil showing the passage of growing of pollen tube up to its destination.3
14. How does gain or loss of chromosome(s) takes place in humans? Describe oneexample each of chromosomal disorder along with the symptoms involving an autosome and a sex chromosome.
A small stretch of DNA that codes for a polypeptide is given below 3′— — — — CAT CAT AGA TGA AAC— — — — 5′
a.) Which type of mutation could have occurred in each type resulting in the following mistakes during replication of the above original sequence?
i. 3`… … … …CAT CAT AGA TGA ATC… … …5`
ii. 3`… … … …CAT ATA GAT GAA AC… … … 5`
b.) How many amino acids will be translated in each of the above two cases?

15. “Apomixes is a form of asexual reproduction that mimics sexual reproduction in plants”. Explain with the help of a suitable example.

6. a.) State the hypothesis which S.L. Miller tried to prove in the laboratory with the help of the set up given above.
b.) Name the organic compound observed by him in the liquid water after running the above experiment.
c.) A scientist simulated a similar set up and added CH4, NH3 and water vapour at 800 ?. Which important component is missing in his experiment?

17. b.) A polypeptide consists of 14 different amino acids.
i) How many base pairs must be there in the processed mRNA that codes for this polypeptide?
ii) How many different types of tRNA are needed for the synthesis of this polypeptide? 3

8. How can inbreeding be both advantageous and disadvantageous in cattle breeding programme? (Mention any two advantages and two disadvantages )
19. “Specific Bt Toxin gene is incorporated into cotton plant so as to control infestation of Bollworm”. Mention the organism from which the gene was isolated and explain its mode of action. 3
20. State any two criteria for determining biodiversity hotspots. Name any two hotspots designated in India.

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