Protein X is found to bind to a certain gene's promoter only when substance A is not present.The gene can be transcribed in the presence of both X and A.It is not transcribed in the presence of X alone.Protein X is a(n)________.Substance A is a(n)________.
A)repressor;inducer
B)repressor;corepressor
C)activator;inducer
D)activator;corepressor

Question

Quizplus · Accepted Answer

Protein X acts as a repressor as it prevents the transcription of the gene in its presence alone. Substance A acts as an inducer as it allows the transcription of the gene in the presence of both X and A. Therefore, the correct choice is A, which indicates "repressor;inducer."

Protein X Is Found to Bind to a Certain Gene's