Science (English Medium) कक्षा १२ - CBSE Important Questions

Read the paragraph given below and answer and questions that follow:

1. Taq polymerase after its discovery replaced E.coli DNA polymerase in PCR technique. Explain giving reasons why was the need felt for the change?
2. What is a primer and its importance in PCR?
3. Write the importance of PCR as a diagnostic tool.

Read the following paragraph and answer the questions that follow:

1. Name the human disease for which the gene therapy was used for the first time.
2. Explain the steps of gene therapy carried to cure the disease using the lymphocytes of the patient. Why is this therapy not a permanent cure of the disease?
3. Write the possible permanent cure of the disease by the gene therapy that is in progress. 

Assertion (A): Synthetic oligonucleotide polymers are used during Annealing in a PCR.

Reason (R): The primers bind to the double stranded DNA at their complementary regions.

Write the scientific name of the source organism of the thermostable DNA polymerase used in PCR.

State the advantage of using Thermostable DNA polymerase.

Bioreactors are the containment vehicles of any biotechnology-based production process. For large scale production and for economic reasons the final success of biotechnological process depends on the efficiency of the bioreactor.

Answer the following questions w.r.t. the given paragraph:

1. List the operational guidelines that must be adhered to so as to achieve optimisation of the bioreactor system. Enlist any four.
2. Mention the phase of the growth we refer to in the statement "Optimisation of growth and metabolic activity of the cells".
3. Is the biological product formed in the bioreactor suitable for the intended use immediate? Give reason in support of your answer.

'EcoRI' has played a very significant role in rDNA technology.

1. Explain the convention for naming EcoRI.
2. Write the recognition site and the cleavage sites of this restriction endonuclease.

What are the protruding and hanging stretches of DNA produced by these restriction enzymes called? Describe their role in the formation of rDNA.

How have transgenic animals proved to be beneficial in production of biological products?

How have transgenic animals proved to be beneficial in chemical safety testing?

What is mutualism?

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

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

Study the graph given below and answer the questions that follow :

(i) Write the status of food and space in the curves (a) and (b).
(ii) In the absence of predators, which one of the two curves would appropriately depict the prey population?
(iii) Time has been shown on X-axis and there is a parallel dotted line above it. Give the significance of this dotted line

How does an age pyramid for human population at given point of time helps the policy-makers in planning for future.

"Analysis of age-pyramids for human population can provide important inputs for long-term planning strategies." Explain.

State Gause’s competitive exclusion principle.

Describe the mutual relationship between fig tree and wasp and comment on the phenomenon that operates in their relationship.

Define the following term:

Commensalism

What is an age-pyramid?