E. coli can synthesize the amino acid threonine or absorb it from the environment. In the thr operon, the repressor is active when it is bound to threonine. If an E. coli bacterium is in an environment where threonine is absent, will transcription of threonine synthesis genes take place? Why or why not?

Question

Avah Mclaughlin

Biology

21 June, 21:01

E. coli can synthesize the amino acid threonine or absorb it from the environment. In the thr operon, the repressor is active when it is bound to threonine. If an E. coli bacterium is in an environment where threonine is absent, will transcription of threonine synthesis genes take place? Why or why not?

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Answers (1)

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Kelly Bartlett · Answer 1

Yes, the synthesis of threonine occurs because threonine will not be bound to the repressor, so in unbound state, the repressor will be inactive.

Explanation:

1. If an E. coli bacterium is grown, in an environment where threonine is absent, transcription of threonine synthesis genes take place, because threonine will not be bound to the repressor, so the repressor will be inactive.

2. When the repressor is bound to the threonine, it becomes active, and in the absence of threonine, repressor become inactive because there is no threonine to bind with repressor.

3. So, in the absence of threonine, there is synthesis of threonine occurs.