Q19 of 27 Page 1

“Specific Bt Toxin gene is incorporated into cotton plant so as to control infestation of Bollworm”. Mention the organism from which the gene was isolated and explain its mode of action.

Bacillus thuringiensis is the bacteria from which the Bt toxin gene was isolated. The Bt toxin gene is coded by the genes cryIAc and cryIIAb.

• Bacillus thuringiensis forms crystals containing a toxic called insecticidal Crystal protein.


• When this inactive Bt toxin is ingested by the insect, it is converted into an active form.


• Due to the alkaline pH conditions of the gut of the insect, the toxin crystals get solubilised.


• The activated toxin then binds to the epithelial cells present on the surface of the gut.


• They create pores that causes the cells to swell and break/lyse, eventually killing the insect.


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17

(a)


b) A polypeptide consists of 14 different amino acids.


i) How many base pairs must be there in the processed mRNA that codes for this polypeptide?


ii) How many different types of tRNA are needed for the synthesis of this polypeptide?


 18

How can inbreeding be both advantageous and disadvantageous in cattle breeding programme? (Mention any two advantages and two disadvantages)

 20

State any two criteria for determining biodiversity hotspots. Name any two hotspots designated in India.

OR


Differentiate between in-situ and ex-situ approaches for conserving biodiversity. Give an example for each.


 21

When the gene product is required in large amounts, so transformed bacteria with the plasmid inside the bacteria are cultured on a large scale in an industrial fermenter which then synthesizes its protein. This product is extracted from the fermenter for commercial use.

a) Why is the used medium drained out from one side while fresh medium is added from the other?


(b) List any four optimum conditions for achieving the desired product in a bioreactor.