CBSE Class 12 Biology Solved Question Paper 2014

Short Answer Type

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State how Agrobacterium tumifaciens has been made a useful cloning vector to transfer DNA to plant cells.

Agrobacterium is a pathogen that affects several dicots and delivers a piece of DNA known as ‘T-DNA’ to transform normal cells to tumor cells. This potential of Agrobacterium has been used to transfer desired gene into the plant. The desired gene is inserted in the T-DNA region and the bacterium is allowed to infect the plant. In this way, the desired changes are made in the plant.

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    Write the types of sex-determination mechanisms the following crosses show. Give an example of each type


    (i) Female XX with Male XO

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    Explain with the help of a suitable example the naming of a restriction endonuclease.

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    How are 'sticky ends' formed on a DNA strand? Why are they so called?

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    Construct an age pyramid which reflects a stable growth status of human population.

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    Explain the basis on which he arrived at this conclusion.

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    State the disadvantage of inbreeding among cattle. How it can be overcome?

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    Write the types of sex-determination mechanisms the following crosses show. Give an example of each type


    (ii) Female ZW with Male ZZ

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    Apart from being a part of the food chain, predators play other important roles. Mention any two such roles supported by examples.

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    Name the scientist who suggested that the genetic code should be made of a combination of three nucleotides.

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