CBSE Class 12

Pre Boards

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Sample Papers

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 Multiple Choice QuestionsLong Answer Type



(a) Name the technology that has helped scientists to propagate on a large scale the desired crops in a short duration. List the steps carried out to propagate the crops by the said technique.

(b) How are somatic hybrids obtained?

(a) Tissue culture is the technique that has helped scientists propagate the desired crops on a large scale in a short duration. The following steps are carried out to propagate crops by tissue culture:

i) Tissue culture is the process of developing a complete plant from a part of a plant. The plant part is called an explant.

ii) Explants can be grown in sterile conditions in special nutrient media to regenerate complete plants.

iii) Nutrient media contain a carbon source (such as sucrose), organic salts, vitamins, amino acids and phytohormones.

iv) Hence, propagation is achieved for a large number of plants in a short duration. This process is called micro propagation.

v) All the plants obtained by tissue culture are called somaclones since they are genetically identical to each other as well as the parent plant.

(b) Somatic hybrids are obtained by the method of somatic hybridisation. In this method, the somatic parts of two plants are hybridised. Protoplasts are isolated and fused to get a hybrid protoplast that grows further to form a new plant. For example, protoplasts of potato and tomato have been actually fused to form a pomato. But this plant is not commercially viable, as it does not have all the desired combination of characteristics for its commercial utilization



(a) Cancer is one of the most dreaded diseases. Explain 'Contact inhibition' and 'Metastasis' with respect to the disease.

 (b) Name the group of genes that have been identified in normal cells that could lead to cancer. How do these genes cause cancer?

 (c) Name any two techniques that are useful in detecting cancers of internal organs.

(d) Why are cancer patients often given I interferon as part of the treatment?