Science (English Medium) Class 12 - CBSE Important Questions

Describe the role of bacterium Thermus aquaticus in carrying the process of polymerase chain reaction.

Answer the following question based on Meselson and Stahl's experiment on E. coli :

Write the name of the chemical substance used as the only source of nitrogen in the experiment.

Name the microbes that help the production of the following product commercially:
Statin

Name the microbes that help the production of the following product commercially:
Citric acid

Name the microbes that help the production of the following product commercially:
Penicillin

State the most important contribution of the following microbes for human welfare:

Monascus purpureus

State the most important contribution of the following microbes for human welfare:

Trichoderma Polysporum

Explain how recombinant human insulin was prepared in 1983 by Eli Lily an American company.

Many members of genus Glomus form a mycorrhizal association with plants. Elaborate how is this association beneficial to the plants.

Organic farmer use Trichoderma as biological control agents. Explain.

Organic farmer use Baculovirus as biological control agents. Explain.

1. Give an example of a genus of fungi that forms mycorhizal association with plants. 
2. How does the plant derive benefits from this association?

Eli Lilly's contribution for diabetic patients through r-DNA technology has been overwhelmingly accepted. Explain how?

• Assertion: PCR is a powerful technique to identify genetic disorders.
• Reason: PCR can detect mutations in low amounts of DNA.

The graph given below indicates the administration of the first (L) and second dose (M) of a vaccine. The corresponding response of the body is indicated by X, and Y. Interpret the graph and explain the reason for such a response shown by the body.

The aeration tank of a sewage treatment plant is not functioning properly. Explain in detail the impact of this on the treatment of sewage and BOD of the effluent.

A farmer grew 2 varieties of corn crops in fields A and B. He grew normal corn crops in field A and GM corn crops in field B. He observed corn borers attacked only in field A. To control it, spores of Bt were sprayed in field A.

1. Name the gene in the spores responsible for the control of this pest.
2. What effect will the spores of Bt have on the insect pest?
3. How has field B developed resistance against this pest?

Name the selectable markers in the cloning vector pBR322. Mention the role they play.

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

Why is the enzyme cellulase needed for isolating genetic material from plant cells and not form the animal cells?