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.

(a) Name the enzyme responsible for the transcription of tRNA and the amino acid the initiator tRNA gets linked with.

(b) Explain the role of initiator tRNA in initiation of protein synthesis.

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22.

State the theory of Biogenesis. How does Miller’s experiment support this theory?

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23.

Name the two different categories of microbes naturally occurring in sewage water. Explain their role in cleaning sewage water into usable water. 


Bacteria and fungi are two categories of naturally occurring microbes present in sewage. The bacteria along with the fungal mycelia form flocs. These flocs are utilised during the secondary treatment of sewage. The primary effluent after separation of the grit and debris is taken to the secondary treatment. Here, the effluent is passed to an aeration tank where it is constantly agitated and air is pumped into it. This leads to vigorous growth of bacteria and floc formation, the bacteria in these flocs consume of organic matter; thus decreasing the BOD of the sewage.

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24.

Write the function of each one of the following:

(a) (Oviducal) Fimbriae

(b) Coleoptile

(c) Oxytocin
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25.

Name the genes responsible for making Bt cotton plants resistant to bollworm attack. How do such plants attain resistance against bollworm attacks? Explain. 

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26.

Study a part of the life cycle of malarial parasite given below. Answer the questions that follow: 




(a) Mention the roles of A in the life cycle of the malarial parasite.

(b) Name the event C and the organ where this event occurs.

(c) Identify the organ B and name the cells being released from it.
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27.

Given below is the representation of amino acid composition not the relevant translated portion of β-chain of hemoglobin, related to the shape of human red blood cells. 





(a) Is this representation indicating a normal human or a sufferer from certain related genetic disease? Give reason in support of your answer.

(b) What difference would be noticed in the phenotype of the normal and the sufferer related to this gene?

(c) Who are likely to suffer more from the defect related to the gene represented the males, the females or both males and females equally? And why?
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28.

By the end of 2002 the public transport of Delhi switched over to a new fuel. Name the fuel. Why is this fuel considered better? Explain.

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29.

Draw a schematic sketch of pBR 322 plasmid and label the following in it:

(a) Any two restriction sites.

(b) Ori and rop genes.

(c) An antibiotic resistant gene.

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 Multiple Choice QuestionsLong Answer Type

30.

Explain the carbon cycle with the help of a simplified model. 

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