Question

Consider the regulation of galactose metabolism through GAL4. Which of the following would result from a mutation that allowed GAL3 to bind to GAL80 in the absence of galactose?
A. There would be no change in the regulation of galactose metabolism because GAL3 normally binds to GAL80 to cause a conformation change in GAL80.
B. GAL80 would no longer be able to stimulate transcription of the genes involved in galactose metabolism.
C. GAL80 would be able to bind to GAL4, and transcription of the genes involved in galactose metabolism would be repressed.
D. Transcription of the genes involved in galactose metabolism would occur both in the presence and in the absence of galactose.
E. GAL4 would no longer be able to bind to the DNA thus, transcription of the genes involved in galactose metabolism would occur.

Answer 1

Answer: Option C.

GAL80 would be able to bind to GAL4, and transcription of the genes involved in galactose metabolism would be repressed.

Explanation:

Gal 3, Gal 80 and Gal 4 are form of proteins which participate in metabolism. They constitute a galactose-responsive switch for the GAL genes When galactose is absent, Gal 80 bind to Gal 4, masking the Gal4AD prevent gene transcription and prevents Gal4-mediated promoter activation