Q22 of 42 Page 1

State the medicinal value and the bioactive molecules produced by Penicilliumnotatum, Monascusperpureus and Trichodermapolysporum.

• Penicillin is an antibiotic that is obtained from mould Penicillium notatum.


• Cyclosporin A bioactive molecule is used as an immunosuppressive agent in organ-transplant patients which is produced by the fungus Trichoderma polysporum.


• Statins produced by the yeast Monascus purpureus that acts by inhibiting the enzyme responsiblefor the synthesis of cholesterol that is blood-cholesterollowering agents.


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20

Name the genus to which baculoviruses belong. Describe their role in the integrated pest management programmes.

 21

Give reasons why:

(a) DNA cannot pass into a host cell through the cell membrane.


(b) Proteases are added during isolation of DNA for genetic engineering.


(c) Single cloning site is preferred in a vector.


 23

Describe the roles of (a) high temperature, (b) primers, and (c) bacterium Thermus aquaticus in carrying the process of polymerase chain reaction.

OR


How does β-galactosidase coding sequence act as a selectable marker? Why is it a preferred selectable marker to antibiotic resistance genes? Explain.


 24

Answer the following questions based on Meselson and Stahl’s experiment on E. coli:

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


(b) Why did they allow the synthesis of the light and the heavy DNA molecules in the organism?


(c) How did they distinguish the heavy DNA molecules from the light DNA molecules? Explain.


(d) Write the conclusion the scientists arrived at, at the end of the experiment.