Plant Tissue Culture

Step 1: Understanding meristem culture.
Meristem culture involves culturing the meristematic tissues of plants. These tissues are undifferentiated and can be used to propagate virus-free plants since they do not carry the viral load found in older tissues.
Step 2: Analyzing the options.
(1) Tall plants: This is incorrect. Meristem culture is not typically used to create tall plants, but rather to propagate virus-free plants.
(2) Disease resistant plants: This is incorrect. While meristem culture helps in producing virus-free plants, it is not specifically used for disease resistance.
(3) Virus free plants: Correct — Meristem culture is specifically used to propagate virus-free plants, as the meristematic tissue is typically free of infections.
(4) Hybrid plants: This is incorrect. Meristem culture is not focused on producing hybrid plants, but rather healthy, virus-free plants.
Step 3: Conclusion.
The correct answer is (3) Virus free plants, as meristem culture is commonly used for this purpose.

Step 1: Understanding the two-hybrid system.
In the two-hybrid system, the goal is to test for protein-protein interactions. The bait protein is fused to a DNA binding domain, and the prey protein is fused to an activation domain. Both proteins are expressed in the cell to assess if they interact, activating the reporter gene.
Step 2: Analyzing the options.
(1) Bait protein: This alone would not activate the reporter gene. It requires interaction with the prey protein.
(2) Prey protein: This alone would not activate the reporter gene. It needs the bait protein to interact.
(3) Both bait and prey protein: Correct — Both proteins need to be present in the cell to test for interaction, which will activate the reporter gene.
(4) Either one of them: This is incorrect because both proteins need to interact to activate the reporter gene.
Step 3: Conclusion.
The correct answer is (3) Both bait and prey protein, as both are necessary for activating the reporter gene in a two-hybrid system.