Subject

Biology

Class

CBSE Class 12

Pre Boards

Practice to excel and get familiar with the paper pattern and the type of questions. Check you answers with answer keys provided.

Sample Papers

Download the PDF Sample Papers Free for off line practice and view the Solutions online.
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 Multiple Choice QuestionsShort Answer Type

21. How does industrial melanism support Darwin’s theory of Natural Selection? Explain.
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22. List the salient features of double helix structure of DNA. 
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23. How are the structural genes activated in the lac operon in E.coli
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24. Trace the life-cycle of malarial parasite in the human body when bitten by an infected female Anopheles. 
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25.

(a) Tobacco plants are damaged severely when infested with Meloidegyne incognitia. Name and explain the strategy that is adopted to stop this infestation.

(b) Name the vector used for introducing the nematode specific gene in tobacco plant.
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26.

(a) Explain the phenomena of multiple allelism and co-dominanace taking ABO blood group as an example.

(b) What is the phenotype of the following:

(i) IAi

(ii) i i

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27.

(a) List any three ways of measuring population density of a habitat.

(b) Mention the essential information that can be obtained by studying the population of an organism. 
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28. How is the amplification of a gene sample of interest carried out using Polymerase Chain Reaction (PCR)? 


Polymerase Chain Reaction or PCR is used to amplify the gene of interest. In this method -:

Primers are designed according to the sequence of the gene of interest.

 Two sets of primers (chemically synthesized oligonucleotide stretches) that are complementary to the gene of interest, DNA polymerase enzyme, and deoxynucleotides are added to the PCR mixture.

PCR consists of 3 steps:

i. Denaturation The ds DNA is denatured by providing high temperature. Taq DNA polymerase isolated from the thermophilic bacteria, Thermus aquaticus (Taq), which  does not degrade at such high temperatures is used.


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29.

(a) What is the programme called that is involved in improving success rate of production of desired hybrid and herd size of cattle?

(b) Explain the method used for carrying this programme for cows. 
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 Multiple Choice QuestionsLong Answer Type

30.

(a) Explain the significance of ecological pyramids with the help of an example.

(b) Why are the pyramids referred to as upright or inverted?
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