Consider statements about biotechnology: 1. Agrobacterium tumefaciens is a natural plant genetic engineer. 2. Bt toxin is active in the acidic gut of insects. 3. RNAi is used to silence specific genes. Which are correct? MCQ with Answer and Explanation

Question

Consider statements about biotechnology: 1. Agrobacterium tumefaciens is a natural plant genetic engineer. 2. Bt toxin is active in the acidic gut of insects. 3. RNAi is used to silence specific genes. Which are correct?

A. 1 and 2 only

B. 2 and 3 only

C. 1, 2 and 3

D. 1 and 3 only

Answer: Option D

Solution (By JKSSB Mock Tests)

Agrobacterium tumefaciens is a soil bacterium that naturally transfers a segment of its Ti plasmid into plant cells, making it a natural genetic engineer used to create transgenic plants. RNA interference (RNAi) is a cellular defense mechanism used in biotechnology to silence specific mRNA molecules, preventing gene expression. Bt toxin is inactive in the insect gut until it encounters the alkaline pH, which solubilizes and activates it. Thus, statements 1 and 3 are correct.

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The vitamin that functions as an antioxidant and is required for the synthesis of collagen is:

A. Vitamin A

B. Vitamin C

C. Vitamin K

D. Vitamin D

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Correct Answer: Option B

Explanation:
Vitamin C (ascorbic acid) is a water-soluble antioxidant that also acts as a cofactor for enzymes involved in collagen synthesis, carnitine synthesis, and neurotransmitter production. Deficiency causes scurvy. Vitamin A is for vision, D for bone, K for clotting. Smokers require higher vitamin C intake due to oxidative stress.

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Question #2

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The pressure that develops in roots due to active absorption of minerals and water is:

A. Wall pressure

B. Root pressure

C. Turgor pressure

D. Transpiration pull

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Correct Answer: Option B

Explanation:
Root pressure is the positive hydrostatic pressure developing in the xylem of roots due to active transport of ions into the vascular cylinder, drawing water osmotically. It can cause guttation in some plants. Transpiration pull is the main driving force for water ascent. Turgor pressure is the pressure of cell contents against the cell wall.

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Question #3

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Which of the following statements about the food web is correct?

A. Energy flow in a food web is cyclic.

B. A food web consists of a single linear chain.

C. It represents interconnected food chains.

D. Decomposers are not part of food webs.

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Correct Answer: Option C

Explanation:
A food web is a network of food chains, showing multiple feeding relationships. Energy flow is unidirectional, and decomposers are integral.

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