Given below is the diagram of agarose gel kept under UV light:

(a) Mark the positive and negative terminals.

(b) What is the charge carried by DNA molecule and how does it help in its separation?

(c) How are the separated DNA fragments finally isolated?

OR

CryIAb is introduced in a plant to prevent infestation by corn borer.

(a) What is the resultant plant referred to as?

(b) Summarize the action of the gene introduced.

(a)

(b) The charge carried by the DNA molecules is negative. They can be separated by placing them under electric field in a matrix which is basically agarose gel. The negatively charged DNA molecules move towards the anode.

(c) The DNA fragments which are separated cannot be cannot be seen with the naked eye unless they are stained. The separated DNA is stained using Ethidium bromide, later followed by exposure to UV light. UV light is used as DNA cannot be seen in white light. After following the above staining method, orange coloured bands of DNA can be seen. Then the DNA bands are cut out from the agarose gel and purified.

OR

(a) The resultant plant is referred to as GMO or Genetically Modified Organisms. It is so called as its gene has been modified by the introduction of cry1ab gene. Genetically modified plants prove to be very useful as they can tolerate varied environmental conditions like cold, drought, heat etc. They reduce the usage of various harmful pesticides and insecticides. They also increase the percentage of nutrients like vitamins, minerals etc.

(b) The gene introduced is cry1ab which encodes for the pesticidal crystal protein CryIAb . It is obtained from Bacillus thuringiensis. This gene cause lysis of the epithelial cells of the midgut of many lepidopteran larvae. The toxic part of the protein is placed at the N-terminal. It is used for maize plant. The protein has insecticidal property.