Final answer:
The yeast two-hybrid system uses two different selectable markers in the expression vectors to ensure that each yeast cell contains both the Gal4 activation domain and the Gal4 binding domain. This is critical for successful protein-protein interaction detection.option d is correct answer.
Step-by-step explanation:
The student has asked about the yeast two-hybrid system, which is a molecular biology tool used to detect protein-protein interactions. Each expression vector in this system must contain a different selectable marker, and the importance of this lies in the ability to ensure that each yeast cell harbors both vectors: one with the Gal4 binding domain (BD) and one with the Gal4 activation domain (AD). This selection process is critical because transcription of a reporter gene only occurs when the prey protein (attached to the AD) interacts with the bait protein (attached to the BD).
If the interaction occurs, it brings the BD and AD in close proximity, allowing transcription to be initiated, leading to the expression of the reporter gene that can beeasilyidentified.Considering that two different selectable markers are used, the correct answer to the question is (d) all recovered colonies will contain both the Gal4 activation domain AND the Gal4 binding domain.
Cells that do not contain both expression vectors will not survive the selection process because each vector provides resistance to a different antibiotic or growth condition. Only those cells that successfully contain both vectors will exhibit resistance to both selectable markers, allowing for their identification and survival.